Nano memory device

ABSTRACT

A non-volatile memory circuit in embodiments of the present invention may have one or more of the following features: (a) a logic source, and (b) a semi-conductive device being electrically coupled to the logic source, having a first terminal, a second terminal and a nano-grease with significantly reduced amount of carbon nanotube loading located between the first and second terminal, wherein the nano-grease exhibits non-volatile memory characteristics.

PRIORITY STATEMENT

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/656,862, filed on Apr. 12, 2018, titled NANO MEMORY DEVICE, U.S.Provisional Patent Application No. 62/656,725 filed on Apr. 12, 2018titled CONDUCTIVE GREASE WITH ENHANCED THERMAL OR ELECTRICALCONDUCTIVITY AND REDUCED AMOUNT OF CARBON PARTICLE LOADING, and U.S.Provisional Patent Application No. 62/656,773 filed on Apr. 12, 2018titled FLEXIBLE NANO COATING WITH SIGNIFICANTLY ENHANCED ELECTRICAL,THERMAL AND SEMICONDUCTOR PROPERTIES all of which are herebyincorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to electronic devices. Particularly, thepresent invention relates to nano-electronic devices. More particularly,but not exclusively, the present invention relates to nano-electroniccircuits.

BACKGROUND

A memristor (a.k.a., a memory resistor) is a non-linear passivetwo-terminal electrical component relating electric charge and magneticflux linkage. It was envisioned, and its name coined, in 1971 by circuittheorist Leon Chua. According to the characterizing mathematicalrelations, the memristor would operate in the following way: thememristor's electrical resistance is not constant but depends on thehistory of current previously flowing through the device (i.e., itspresent resistance depends on how much electric charge has flowed inwhat direction through it in the past; the device remembers itshistory—the so-called non-volatility property). When the electric powersupply is turned off, the memristor remembers its most recent resistanceuntil it is turned on again.

Chua extrapolated a conceptual symmetry between the non-linear resistor(voltage vs. current), non-linear capacitor (voltage vs. charge) andnon-linear inductor (magnetic flux linkage vs. current). He theninferred the possibility of a memristor as another fundamentalnon-linear circuit element linking magnetic flux and charge. In contrastto a linear (or non-linear) resistor the memristor has a dynamicrelationship between current and voltage including a memory of pastvoltages or currents.

Memristor resistance depends on the integral of the input applied to theterminals (rather than on the instantaneous value of the input as in avaristor). Since the element “remembers” the amount of current lastpassing through, it was tagged by Chua with the name “memristor”.Another way of describing a memristor is as any passive two-terminalcircuit element maintaining a functional relationship between the timeintegral of current (i.e., charge) and the time integral of voltage(i.e., flux, as it is related to magnetic flux). The slope of thisfunction is called the memristance M and is like variable resistance.

A varistor is an electronic component with an electrical resistancevarying with the applied voltage. Also known as a voltage-dependentresistor (VDR), it has a nonlinear, non-ohmic current-voltagecharacteristic like a diode. In contrast to a diode however, it has thesame characteristic for both directions of traversing current. At lowvoltage it has a high electrical resistance which decreases as thevoltage is raised. Varistors are used as control or compensationelements in circuits either to provide optimal operating conditions orto protect against excessive transient voltages. When used as protectiondevices, they shunt the current created by the excessive voltage awayfrom sensitive components when triggered.

With reference to FIGS. 17 & 18A-D are a Simulink Model & plotrepresentation of a variable resistor circuit in accordance with theprior art is shown. As will be discussed in detail below regarding FIG.1, a memristor, memcapacitor and/or meminductor will have a Lissajouscurve where the hysteresis loop degenerates to a straight (linear) orcurved line (non-linear) through the origin (i.e., it does not storeenergy). From the plots of FIGS. 18A-D, it can be seen the varistor doesnot pass through the origin. Furthermore, a varistor will not rememberits last state as will the memristor, memcapacitor and/or meminductordescribed in detail below.

The memristor definition is based solely on the fundamental circuitvariables of current and voltage and their time-integrals, just like theresistor, capacitor and inductor. Unlike those three elements however,which are allowed in linear time-invariant or LTI system theory,memristors of interest have a dynamic function with memory and may bedescribed as some function of net charge. There is no such thing as astandard memristor. Instead, each device implements a function, whereinthe integral of voltage determines the integral of current and viceversa. A linear time-invariant memristor, with a constant value for M,is simply a conventional resistor.

Leon Chua has argued the memristor definition could be generalized tocover all forms of two-terminal non-volatile memory devices based onresistance switching effects. These devices are intended forapplications in nano-electronic memories, computer logic andneuromorphic/neuromemristive computer architectures.

Memcapacitor is a member of a family of new circuit elements postulatedby Chua in the late seventies and presented as one of 4 guest lecturesat the 1978 European Conference on Circuit Theory and Design (ECCTD).Memcapacitor was formally defined by Chua in 2003. The nanoscale circuitelements, i.e., memristor, memcapacitor, and meminductor, have memorialproperties and can store information without power supplies.

Although an actual solid-state memcapacitor has not been yet realized,it is important to design effective memcapacitor models and makeprospective studies for its applications. In 2009, a piecewise linearmemcapacitor model was first presented.

Memcapacitive and meminductive systems are two recently postulatedclasses of circuit elements with memory complementing the class ofmemristive systems. Their main characteristic is a hysteretic loop—whichmay or may not pass through the origin—in their constitutive variables(charge-voltage for memcapacitors and current-flux for meminductors)when driven by a periodic input, and, unlike memristors, they can storeenergy. As of today, a few systems have been found to operate asmemcapacitors and meminductors. However, these are neither available onthe market yet, nor can their properties be easily tuned to investigatetheir role in more complex circuits. The same can be said aboutmemristive systems. Therefore, electronic emulators of such memoryelements easily built and tuned would be highly desirable, so theseproperties can be identified in the future.

Flash memories are currently by far the most widely used type ofnon-volatile memory (NVM), and phase-change memories (PCMs) are the mostpromising emerging NVM technology. Flash memories and PCM have manyimportant common properties, including noisy cell programming, limitedcell endurance, asymmetric cost in changing a cell state in differentdirections, the drifting of cell levels after programming, cellheterogeneities and the like. As representative NVMs, they have been,and likely will continue to be widely used in mobile, embedded andmass-storage systems. They are partially replacing hard drives and mainmemories and are fundamentally changing some computer architectures.

In 2008, a team at HP Labs claimed to have found Chua's missingmemristor based on an analysis of a thin film of titanium dioxide thusconnecting the operation of RRAM devices to the memristor concept.Following this claim, Leon Chua has argued the memristor definitioncould be generalized to cover all forms of two-terminal non-volatilememory devices based on resistance switching effects. In 2015, aself-directed channel ion-conducting memristor was made commerciallyavailable by KNOWN. However, this self-directed channel ion-conductingmemristor has several drawbacks including: a low power threshold (e.g.,much less than 0.1 watts), high sensitivity to ESD, multiple components(i.e., up to 12 standard components), no shipping product level deviceand the 16 pin IC DIP memristor sold by KNOWN can cost as much as $200.

There are several advantages of the memristor memory over conventionaltransistor-based memories. One is its strikingly small size. Thoughmemristor is still at its early development stage, its size is at mostone tenth of its RAM counterparts. If the fabrication technology for thememristor is improved, the size advantage could be even moresignificant. Another feature of the memristor is its incomparablepotential to store analog information, which enables the memristor tokeep multiple bits of information in a memory cell. Besides thesefeatures, the memristor is also an ideal device for implementingsynaptic weights in artificial neural networks

Therefore, what is needed is an efficient and effective way to producenon-volatile memory devices on a nano-scale. Further, what is needed isa nano memory device capable of handling power up to and greater than 4watts. Further, what is needed is a nano memory device not sensitive toESD. Further, what is needed is a nano-scale and one componentnon-volatile memory device. Further, what is needed is an inexpensivenano memory device.

SUMMARY

Therefore, it is a primary object, feature, or advantage of the presentinvention to improve over the state of the art.

A non-volatile memory circuit in embodiments of the present inventionmay have one or more of the following features: (a) a logic source, and(b) a semi-conductive device being electrically coupled to the logicsource, having a first terminal, a second terminal and a nano-greasewith significantly reduced amount of carbon nanotube loading locatedbetween the first and second terminal, wherein the nano-grease exhibitsnon-volatile memory characteristics.

A non-volatile memory circuit in embodiments of the present inventionmay have one or more of the following features: (a) a voltage source,(b) a semi-conductive device being electrically coupled to the logicsource, having a first terminal, a second terminal and a nano-greasewith significantly reduced amount of carbon nanotube loading locatedbetween the first and second terminal, wherein the nano-grease exhibitsnon-volatile memory characteristics, and (c) a voltage sensorelectrically coupled in parallel with the semi-conductive device capableof measuring the voltage drop at the semi-conductive device.

One or more of these and/or other objects, features, or advantages ofthe present invention will become apparent from the specification andclaims follow. No single embodiment need provide every object, feature,or advantage. Different embodiments may have different objects,features, or advantages. Therefore, the present invention is not to belimited to or by any objects, features, or advantages stated herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrated embodiments of the disclosure are described in detail belowwith reference to the attached drawing figures, which are incorporatedby reference herein.

FIG. 1 is a Lissajous curve showingmemristive-memcapacitive-meminductive properties in accordance with anembodiment of the present invention;

FIG. 2 is a sample plot of current vs. voltage curve with 10V point topoint (P-P AC 0.1 Mhz voltage) applied to nano-grease in series with a1K ohm resistor in accordance with an embodiment of the presentinvention;

FIG. 3 is a pictorial representation of nano-grease in accordance withan embodiment of the present invention;

FIG. 4 is a sample plot of current vs. voltage curve with 10V point topoint (P-P AC 10 Mhz voltage) applied to nano-grease materials in serieswith a 1K ohm resistor in accordance with an embodiment of the presentinvention

FIG. 5 is sample plot of current vs. voltage curve with 10V point topoint (P-P AC 0.1 Mhz, 1 Mhz & 10 Mhz voltage) applied to nano-greasematerials in series with a 1K ohm resistor in accordance with anembodiment of the present invention;

FIG. 6 is a Simulink Model representation of the electrical behaviorresponse of nano-grease materials in accordance with embodiments of thepresent invention;

FIG. 7 is a Simulink Model plot of a Simulink Model representation of amemristor circuit and a plot of the electrical response for thenano-grease materials in accordance with an embodiment of the presentinvention;

FIG. 8 is a pictorial representation of a nano-grease memristor circuitin accordance with an embodiment of the present invention;

FIG. 9 is a pictorial representation of a Simulink Model representationof a nano-grease memcapacitor circuit in accordance with an embodimentof the present invention;

FIGS. 10A-D are a Simulink Model plots of a Simulink Modelrepresentation of a memcapacitor circuit and plot for the electricalresponse of the nano-grease materials in accordance with an embodimentof the present invention;

FIG. 11 is a pictorial representation of a nano-grease memcapacitorcircuit in accordance with an embodiment of the present invention;

FIG. 12 is a Simulink Model representation of a power memristor circuitfor a variable DC power supply using a memristor bridge in accordancewith an embodiment of the present invention;

FIGS. 13A-C are Simulink Model plots of a Simulink Model representationof a power memristor circuit for a variable DC power supply using amemristor bridge in accordance with an embodiment of the presentinvention;

FIGS. 14A-C are Simulink Model plots of a Simulink Model representationof a memristor circuit in accordance with an embodiment of the presentinvention;

FIGS. 15A-C are Simulink Model plots of a Simulink Model representationof a memristor circuit in accordance with an embodiment of the presentinvention;

FIG. 16 are Simulink Model plots of a Simulink Model representation of amemristor circuit in accordance with an embodiment of the presentinvention;

FIG. 17 is a Simulink Model representation of a variable resistorcircuit in accordance with the prior art;

FIGS. 18A-D are Simulink Model plots of a Simulink Model representationof a variable resistor circuit in accordance with the prior art;

FIG. 19 are Simulink Model plots of a Simulink Model representation of amemdevice circuit in accordance with an embodiment of the presentinvention;

FIGS. 20A-D are Simulink Model plots of a Simulink Model representationof a memdevice circuit in accordance with an embodiment of the presentinvention; and

FIGS. 21A and B are a Simulink Model and plot of a Simulink Modelrepresentation of a memdevice circuit in accordance with an embodimentof the present invention.

FIG. 22 shows the grease based on 7.5 wt % MWNT-OH/92.5 wt % Ester oil.

FIG. 23 shows a scanning electron microscope (SEM) image of the greasebased on 7.5 wt % MWNT-OH/92.5 wt % Ester oil.

FIGS. 24A-24D shows the friction coefficients exhibited by CNT-basedgreases and three other conventional lubricant greases.

FIGS. 25A and 25B show photographs of an exemplary conductive flexiblecoating composition comprising carbon nanomaterial and providingenhanced conductor/semiconductor properties on a surface.

Some of the figures include graphical and ornamental elements. It is tobe understood the illustrative embodiments contemplate all permutationsand combinations of the various graphical elements set forth in thefigures thereof.

DETAILED DESCRIPTION

The following discussion is presented to enable a person skilled in theart to make and use the present teachings. Various modifications to theillustrated embodiments will be plain to those skilled in the art, andthe generic principles herein may be applied to other embodiments andapplications without departing from the present teachings. Thus, thepresent teachings are not intended to be limited to embodiments shownbut are to be accorded the widest scope consistent with the principlesand features disclosed herein. The following detailed description is tobe read with reference to the figures, in which like elements indifferent figures have like reference numerals. The figures, which arenot necessarily to scale, depict selected embodiments and are notintended to limit the scope of the present teachings. Skilled artisanswill recognize the examples provided herein have many usefulalternatives and fall within the scope of the present teachings. Whileembodiments of the present invention are discussed in terms of powernano memory devices, it is fully contemplated embodiments of the presentinvention could be used in most any nanoscale memory device withoutdeparting from the spirit of the invention.

Embodiments of the present invention can utilize a nano-grease withsignificantly reduced amount of carbon nanotube (SWNT (single wallnanotube), double-walled nanotubes (“DWNT”), and MWNT (multi-wallnanotube)) loading as disclosed in detail below. One embodimentdiscloses a stable conductive grease composition comprising a base oiland nanomaterial, wherein the nanomaterial is a functionalizednanomaterial having one or more of a first functional group capable offorming a hydrogen bond or boron nanomaterial; and wherein the base oilcomprises one or more of a second functional group capable of forming ahydrogen bond with the first function group of the nanomaterial.

In another embodiment, a stable and homogeneous grease based on carbonnanotubes (hereinafter referenced to as CNT) (i.e., single-wall andmulti-wall) in polyalphaolefin oil being produced without using achemical surfactant. For example, for a 22-24 wt % (14-15 vol %)multi-wall CNT loading, the thermal conductivity (TC) of the greaseshows a 70-80% increase compared to no nanotube loading. In addition,the grease is electrically conductive, has a high dropping point, goodtemperature resistance, and does not react with copper at temperaturesup to 177° C. Additional embodiments disclose a new way to produce thegrease with low nanotube loading (SWNT<2.5 wt %, MWNT<1.5 wt % ).

In some embodiments the inventors have made several quality greases bythree roll mills. They are:

7.5 wt % MWNT-OH/92.5 wt % N650HT (FIG. 7)

7.5 wt % MWNT-OH/92.5 wt % PAO

1.4 wt % MWNT-OH/98.6 wt % Krytox

2.5 wt % SWNT-OH/97.5 wt % PAO

The inventors have found all nano-greases produced are stable. No oilleaks are found for these 4 grease samples for at least 10 days. Morephysical properties such as dropping point, penetration length, thermalconductivity, electrical conductivity, rheology behavior, etc. havegreatly improved qualities.

The inventors have discovered the nano-grease with significantly reducedamount of carbon nanotubes (SWNT and MWNT) displays some uniqueelectrical attributes. The inventors have found the nano-grease withsignificantly reduced amount of carbon nanotubes displays electricalattributes common to a memristor, a memcapacitor and a meminductor whichis discussed in greater detail below. The use of this nano-grease withsignificantly reduced amount of carbon nanotubes as a memristor, amemcapacitor and meminductor has great potential in several industries.

They could be implemented as transistors. Nanoparticle composites couldbe combined into devices called crossbar latches, which could replacetransistors in future computers, given their much higher circuitdensity. They can potentially be fashioned into non-volatile solid-statememory, which would allow greater data density than hard drives withaccess times like DRAM, replacing both components. Nanoparticlecomposite applications could include programmable logic, signalprocessing, neural networks, control systems, reconfigurable computing,brain-computer interfaces and RFID.

Nanoparticle composite devices are potentially useful for stateful logicimplication, allowing a replacement for CMOS-based logic computation.Nanoparticle composites could be used for adaptive behavior ofunicellular organisms. For example, subjected to a train of periodicpulses, a circuit learns and anticipates the next pulse like thebehavior of slime molds where the viscosity of channels in the cytoplasmresponds to periodic environment changes. Applications of such circuitsmay include pattern recognition. Neuromorphic architectures may be basedon nanoparticle composite memristive systems. Whole-brain nanoparticlecomposite circuits can power a virtual and robotic agent usingmemristive hardware. Nanoparticle composite memristors can be used asnon-volatile analog memories and can mimic classic habituation andlearning phenomena. According to Allied Market Research the memristormarket was worth $3.2 million in 2015 and will be worth $79.0 million by2022.

With reference to FIG. 1, one of the resulting properties of memristors,memcapacitors and meminductors is the existence of a pinched hysteresiseffect, shown by the Lissajous curve 100, in the voltage-current,voltage-charge and magnetic flux-current plane when driven by anybipolar periodic voltage or current without respect to initialconditions. For a current-controlled memristive system, the input u(t)is the current i(t), the output y(t) is the voltage v(t), and the slopeof the curve M represents the electrical resistance, capacitance orinductance. The change in slope M of the pinched hysteresis curve 102demonstrates switching between different resistance states which is aphenomenon central to ReRAM and other forms of two-terminal resistancememory. The area of each lobe of the pinched hysteresis loop 102 shrinksas the frequency of the forcing signal increases. Memristive theorypredicts the pinched hysteresis effect will degenerate, resulting in astraight-line representative of a linear resistor. As the frequencytends to infinity, the hysteresis loop degenerates to a straight(linear) or curved line (non-linear) through the origin (i.e., it doesnot store energy).

Memcapacitors and meminductors have an almost identical pinchedhysteresis effect and are shown in FIG. 1 as well. Thus, the change inslope M of the pinched hysteresis curve 102 demonstrates switchingbetween different capacitive states for a memcapacitor and a switchingof different inductive states for a meminductor. As with the memristor,theory predicts the hysteresis effect will degenerate into astraight-line representative of a linear capacitor and/or inductor. Thisis because the higher the frequency goes the more the input appears tobe constant and thus the memcapacitor will behave as a standardcapacitor and a meminductor will behave as a standard inductor.

With reference to FIG. 2, a sample plot of current vs. voltage curvewith 10V point to point (P-P AC 0.1 Mhz voltage) applied to thenano-grease 300 with significantly reduced amount of carbon nanotubes(SWNT and MWNT) of FIG. 3, and discussed in detail below, in series witha 1K ohm resistor in accordance with an embodiment of the presentinvention. As can clearly be seen the electrical response of the carbonnanotube structure significantly resembles the Lissajous curve 100 for amemristor. FIG. 2 clearly shows the carbon nanotube structure disclosedin embodiments of the present application have memristive properties andcould be used to implement memristors on a nanoscale.

With reference to FIGS. 4 & 5, sample plots for different testfrequencies of current vs. voltage curve with 10V point to point (P-P ACvoltage) applied to the carbon nanotube structure 300 of FIG. 3 anddiscussed above in series with a 1K ohm resistor. The plots arerecreated at different frequencies getting similar results but differentareas under the curve for the varying frequencies.

With reference to FIGS. 6 & 7 a Simulink Model representation and plotof the electrical behavior of nano-grease materials in accordance withthe present invention is shown. To determine the electrical behavioralproperties of the nano-grease detailed below, the inventors set out tocreate a Simulink Model of a memristor at 0.1 Mhz. Simulink is agraphical programming environment for modeling, simulating and analyzingmultidomain dynamical systems. Its primary interface is a graphicalblock diagraming tool and a customizable set of block libraries. Itoffers tight integration with the MATLAB environment and can eitherdrive MATLAB or be scripted from it. Simulink is widely used inautomatic control and digital signal processing for multidomainsimulation and Model-Based Design.

From the graph shown in FIG. 7, it can be seen the memristive SimulinkModel of FIG. 6 plots almost overtop of the test results on thenano-grease. Thus, the inventors have found a material which providessubstantial memristive properties and can be utilized to createnano-scale memory circuits.

With reference to FIG. 8, a pictorial representation of a circuit havinga nano-grease memristor structure with a significantly reduced amount ofcarbon nanotubes (SWNT and MWNT) in accordance with an embodiment of thepresent invention is shown. Nano non-volatile memory circuit 600 is ageneral and simplified depiction of a non-volatile memory circuit inaccordance with an embodiment of the present invention. As can be seen,logic source 602 is only shown connected to one carbon nanotubememristor 604, however, it is fully contemplated logic source 602 couldbe the input for several nanotube memristors 604 up to tens of trillionsof carbon nanotube memristors 604. Logic source 602 could be most anyinput to a nano non-volatile memory circuit 600 without departing fromthe spirit of the invention.

In the structure of memristor 604, nano-grease 300 is the materialseparating the two terminal conductors.

The logic source 602 may include circuitry, chips and other digitallogic. The logic source 602 may represent hardware, software, firmwareor any combination thereof. In one embodiment, the logic source 602 mayinclude one or more processors. Logic source 602 may also represent anapplication specific integrated circuit (ASIC), system-on-a-chip (SOC)or field programmable gate array (FPGA). In one embodiment, the logicsource 602 is circuitry or logic enabled to control execution of a setof instructions and provide an output to memristor 604. The logic source602 may be one or more microprocessors, digital signal processors,application-specific integrated circuits (ASIC), central processingunits, analog input or other devices suitable for controlling anelectronic device including one or more hardware and software elements,executing software, instructions, programs, and applications, convertingand processing signals and information and performing other relatedtasks. The logic source 602 may be a single chip or integrated withother computing or communications components.

Logic source 602 could be most any level of voltage, such as an analoginput, and could represent binary states (e.g., 1, 0 or 1, 0, −1). Logicsource 602 could be any analog, digital and/or combination sourceproviding the current state of a system. The structure of carbonnanotube memristor 604 having enhanced electrical properties is fullydiscussed in detail above and below. A 1 k ohm resistor 606 is shown inseries with carbon nanotube memristor 604. Voltage sensor 608 is shownin parallel with carbon nanotube memristor 604 and is used to detect thevoltage drop across carbon nanotube memristor 604. The voltage dropacross carbon nanotube memristor 604 will show the state of carbonnanotube memristor 604. E.g., either a high state, a zero state, a lowstate or an analog voltage, current or magnetic flux.

The inventors had additionally found other beneficial properties to thenano-grease described in detail below. Memristor 604 can handlerelatively high-power inputs up to and including greater than 4 Watts.Further, memristor 604 is not sensitive to ESD. The current memristorcell 604 takes up 1 cubic centimeter, which is significantly smallerthan previous designs. Further, the total cost of memristor cell 604 forproduction is $2 per unit; therefore, significantly less expensive thanprevious memristors.

With reference to FIG. 9 a pictorial representation of a Simulink Modelrepresentation of a memcapacitor circuit of the nano-grease materials inaccordance with an embodiment of the present invention is shown. Whatthe inventors have discovered is the nano-grease discussed in detailbelow displays memcapacitive and meminductive properties as well. TheSimulink Model of FIG. 9 shows a sample circuit of a memcapacitivecircuit. With these properties known, it is fully contemplated anano-grease gel cell, such as memristive circuit 604 could be used inmost any memory utility to perform non-static memory functions. It couldfunction as a memristor, memcapacitor or meminductor. The only variablesto decide its function would be the varying input, either voltage ormagnetic flux.

With reference to FIGS. 10A-D Simulink Model plots of a Simulink Modelrepresentation of a memcapacitor circuit and plot for the nano-greasematerials electrical response in accordance with an embodiment of thepresent invention is shown. From the charts on FIGS. 10A-D it can beseen the charge on the memcapacitive cell plots almost on top of theSimulink Model. Thus, the inventors have discovered the nano-greasematerial can be placed in a cell and the materials have capacitiveproperties having a non-volatile memory property. Also, from the plots,it can be shown these properties held up over a period. From plot Awhere the tests were run for 10 seconds, to plot B where the tests wererun for 1 minute 40 seconds, to plot C where the tests were run for 16minutes 40 seconds and finally to plot D where the tests were run for 2hours 46 minutes and 28 seconds it can be shown the nano-grease materialholds its non-volatile memory capacity over time as well.

With reference to FIG. 11 a pictorial representation of a nano-greasememcapacitor circuit in accordance with an embodiment of the presentinvention is shown. Memcapacitive gel cell circuit 1100 may have an ACvoltage source 1102, a resistor 1104, a memcapacitive gel cell 1108 anda voltage sensor 1106 in a most simplified and basic sense.Memcapacitive gel cell circuit 1100 is a general and simplifieddepiction of a non-volatile memory circuit in accordance with anembodiment of the present invention. As can be seen, AC voltage source1102 is only shown connected to one memcapacitor gel cell 1108, however,it is fully contemplated AC voltage source 1102 could be the input forseveral memcapacitive gel cells 1108 up to tens of trillions ofmemcapacitive gel cells 1108. AC voltage source 1102 could be most anyvarying voltage, current or magnetic flux input to a nano non-volatilememory circuit without departing from the spirit of the invention.

In the structure of memcapacitor gel cell 1108, nano-grease 300 is thedielectric within the capacitor. In the structure of meminductor,nano-grease 300 is the core within the inductor.

AC voltage source 1102 could be most any level of voltage, such as ananalog input, and could represent binary states (e.g., 1, 0 or 1, 0,−1). A 1 k ohm resistor 1104 is shown in series with memcapacitive gelcell 1108. Voltage sensor 1106 is shown in parallel with memcapacitivegel cell 1108 and is used to detect the charge across memcapacitive gelcell 1108. The charge on memcapacitive gel cell 1108 will show the stateof memcapacitive gel cell 1108. E.g., either a high state, a zero state,a low state or an analog voltage, current or magnetic flux.

With reference to FIG. 12 a Simulink Model representation of a powermemristor circuit for a variable DC power supply using a memristorbridge in accordance with an embodiment of the present invention isshown. Power memristor circuit 1200 for a variable DC power supply usinga memristor bridge 1202. Power memristor circuit 1200 can be controlledby DC offsets in the driving signal and the sinusoidal AC power source1204 could also be substituted with an AC pulse width modulation (PWM)source for greater power efficiency.

With reference to FIGS. 13A-C are Simulink Model plots of a SimulinkModel representation of a power memristor circuit for a variable DCpower supply using a memristor bridge in accordance with an embodimentof the present invention is shown. The plots of FIG. 13 verify thefunctionality of the memristor circuit 1200. Several DC output setpointsare shown having successfully achieved varying DC outputs.

FIGS. 14A-C are Simulink Model plots of a Simulink Model representationof a memristor circuit in accordance with an embodiment of the presentinvention is shown. FIG. 14 shows plots verifying the memristor circuitsdiscussed above provide non-volatile memory. Moreover, the plots in FIG.14 show the nano-grease 300 resistance is a function of the appliedelectric potential and/or current history of the device. It'sinteresting to note, the slow change in voltage curve (1400) varies fromthe fast change in voltage curve (1402), but when the voltage variationreturns to a similar pattern the curves converge together over time. Ina non-memory device, any change would simply track the same curve(albeit at a different rate). In a similar fashion, rapid changes ofvoltage are deviations from the slow variation curve but converge to thelimit cycle when it returns to its sinusoidal pattern.

With reference to FIGS. 15A-C & 16 Simulink Model plots of a SimulinkModel representation of a memristor circuit in accordance with anembodiment of the present invention is shown. FIGS. 15 and 16 showexamples of nano-grease 300 consistence over variations in appliedamplitudes.

With reference to FIGS. 19, 20A-D & 21A & B, Simulink Model plots of aSimulink Model representation of a memdevice circuit in accordance withan embodiment of the present invention are shown. The memresistor,memcapacitor and meminductor of the present invention exhibit what iscalled a type two pinched hysteresis curve which is unique formemdevices. Standard memdevices are type one meaning they follow afigure eight crossing pattern through the origin, while the memdevicesof embodiments of the current invention would be classified as a typetwo. Further, the memdevice of the embodiments of the current inventionexhibit a charging style and dis-charging style curve as shown in FIG.19. Further, FIG. 21B shows a modeled charging curve reproducing thememdevice's voltage-current curves shown in FIG. 20.

Conductive greases have been prepared using carbon nanotubes for avariety of applications. They have been found to be particularly goodthermal transfer fluids. Such compositions have required relatively highconcentrations of carbon nanotubes, e.g., greater than 15 wt. % or evengreater than 20 wt. %. As disclosed in U.S. Pat. No. 7,871,533, a stableand homogeneous grease based on carbon nanotubes (CNTs, single-wall andmulti-wall) in polyalphaolefin oil has been produced without using achemical surfactant. For example, with a 22-24 wt % (14-15 vol %)multi-wall CNT loading, a grease has a thermal conductivity (TC) 70-80%increase compared to one with no nanotube loading. In addition, such agrease has a high dropping point, good temperature resistance, and doesnot react with copper at temperatures up to 177° C.

However, such a grease with a high carbon nanotube loading has a lowelectrical conductivity and has proven to be difficult for use inelectrical applications. Thus, there is a need to prepare greasecompositions have both stability and improved electrical conductivity.

Accordingly, it is an objective of the present disclosure to develop astable nanogrease composition with an improved thermal and/or electricalconductivity.

A further object of the invention is to provide a grease compositionwith low carbon nanotube loading (<2 wt % ) and improved thermal and/orelectrical properties.

Other objects, advantages and features of the present invention willbecome apparent from the following specification taken in conjunctionwith the accompanying figures.

An advantage of the invention is enhanced thermal and/or electricalconductivity of the disclosed grease compositions. It is an advantage ofthe present invention the conductive greases have unexpectedly improvedelectrical conductivity. This is particularly surprising given the lowweight percentage loading of carbon particles.

In one aspect, disclosed herein is a stable conductive greasecomposition comprising a base oil and nanomaterial, wherein thenanomaterial is a functionalized nanomaterial having one or more of afirst functional group capable of forming a hydrogen bond or boronnanomaterial; and wherein the base oil comprises one or more of a secondfunctional group capable of forming a hydrogen bond with the firstfunction group of the nanomaterial.

In another aspect, the present disclosure is a method of enhancingthermal or electric conductivity of a grease composition, the methodcomprises adding into a grease composition a nanomaterial to form animproved grease composition, wherein the nanomaterial is afunctionalized carbon nanomaterial having one or more of a firstfunctional group capable of forming a hydrogen bond with a secondfunctional group in the grease composition or boron nanomaterial.

While multiple embodiments are disclosed, still other embodiments of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the invention. Accordingly, the figures anddetailed description are to be regarded as illustrative in nature andnot restrictive.

Various embodiments of the present invention will be described in detailwith reference to the figures. Reference to various embodiments does notlimit the scope of the invention. Figures represented herein are notlimitations to the various embodiments according to the invention andare presented for exemplary illustration of the invention.

The present invention relates to conductive greases comprising carbonparticles. The conductive greases have many advantages over existingnanogreases. For example, the conductive greases have significantlyimproved electrical conductivity over nanogreases used in manyelectrical transfer fluid applications. Furthermore, these improvementsoccur with a reduction in the amount of carbon added to the conductivegrease when compared to existing conductive greases comprising carbonnanotubes. This improvement is unexpected given the reduction in carbonloading as carbon nanotubes are conductive. Additionally, it waspreviously seen thermal conduction properties for thermal nanofluidscomprising carbon nanotubes were increased with increasingconcentrations of carbon nanotubes.

Definitions

So, the present invention may be more readily understood, certain termsare first defined. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as commonlyunderstood by one of ordinary skill in the art to which embodiments ofthe invention pertain. Many methods and materials similar, modified, orequivalent to those described herein can be used in the practice of theembodiments of the present invention without undue experimentation, thepreferred materials and methods are described herein. In describing andclaiming the embodiments of the present invention, the followingterminology will be used in accordance with the definitions set outbelow. Moreover, the embodiments of this invention are not limited toparticular electrical conductive grease applications, which can vary andare understood by skilled artisans. It is further to be understood allterminology used herein is for the purpose of describing embodimentsonly and is not intended to be limiting in any manner or scope.

As used in this specification and the appended claims, the singularforms “a,” “an” and “the” can include plural referents unless thecontent clearly indicates otherwise. Further, all units, prefixes, andsymbols may be denoted in its SI accepted form.

Numeric ranges recited within the specification are inclusive of thenumbers defining the range and include each integer within the definedrange. Throughout this disclosure, various aspects of this invention arepresented in a range format. The description in range format is merelyfor convenience and brevity and should not be construed as an inflexiblelimitation on the scope of the invention. Accordingly, the descriptionof a range should be considered to have specifically disclosed all thepossible sub-ranges, fractions, and individual numerical values withinrange. For example, description of a range such as from 1 to 6 should beconsidered to have specifically disclosed sub-ranges such as from 1 to3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc.,as well as individual numbers within range, for example, 1, 2, 3, 4, 5,and 6, and decimals and fractions, for example, 1.2, 3.8, 1½, and 4¾This applies regardless of the breadth of the range.

The term “about,” as used herein, refers to variation in the numericalquantity can occur, for example, through typical measuring techniquesand equipment, with respect to any quantifiable variable, including, butnot limited to, mass, volume, time, distance, wave length, frequency,voltage, current, and electromagnetic field. Further, given solid andliquid handling procedures used in the real world, there is certainerror and variation is likely through differences in the manufacture,source, or purity of the ingredients used to make the compositions orcarry out the methods and the like. The term “about” also encompassesthese variations. Whether or not modified by the term “about,” theclaims include equivalents to the quantities.

The methods and compositions of the present invention may comprise,consist essentially of, or consist of the components and ingredients ofthe present invention as well as other ingredients described herein. Asused herein, “consisting essentially of” means the methods, systems,apparatuses and compositions may include additional steps, components oringredients, but only if the additional steps, components or ingredientsdo not materially alter the basic and novel characteristics of theclaimed methods, systems, apparatuses, and compositions.

As used herein, the term “alkyl” or “alkyl groups” refers to saturatedhydrocarbons having one or more carbon atoms, including straight-chainalkyl groups (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,octyl, nonyl, decyl, etc.), cyclic alkyl groups (or “cycloalkyl” or“alicyclic” or “carbocyclic” groups) (e.g., cyclopropyl, cyclopentyl,cyclohexyl, cycloheptyl, cyclooctyl, etc.), branched-chain alkyl groups(e.g., isopropyl, tert-butyl, sec-butyl, isobutyl, etc.), andalkyl-substituted alkyl groups (e.g., alkyl-substituted cycloalkylgroups and cycloalkyl-substituted alkyl groups).

Unless otherwise specified, the term “alkyl” includes both“unsubstituted alkyls” and “substituted alkyls.” As used herein, theterm “substituted alkyls” refers to alkyl groups having substituentsreplacing one or more hydrogens on one or more carbons of thehydrocarbon backbone. Such substituents may include, for example,alkenyl, alkynyl, halogeno, hydroxyl, alkylcarbonyloxy, arylcarbonyloxy,alkoxycarbonyloxy, aryloxy, aryloxycarbonyloxy, carboxylate,alkylcarbonyl, arylcarbonyl, alkoxycarbonyl, aminocarbonyl,alkylaminocarbonyl, dialkylaminocarbonyl, alkylthiocarbonyl, alkoxyl,phosphate, phosphonato, phosphinato, cyano, amino (including alkylamino, dialkylamino, arylamino, diarylamino, and alkylarylamino),acylamino (including alkylcarbonylamino, arylcarbonylamino, carbamoyland ureido), imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate,sulfates, alkylsulfinyl, sulfonates, sulfamoyl, sulfonamido, nitro,trifluoromethyl, cyano, azido, heterocyclic, alkylaryl, or aromatic(including heteroaromatic) groups.

In some embodiments, substituted alkyls can include a heterocyclicgroup. As used herein, the term “heterocyclic group” includes closedring structures analogous to carbocyclic groups in which one or more ofthe carbon atoms in the ring is an element other than carbon, forexample, nitrogen, sulfur or oxygen. Heterocyclic groups may besaturated or unsaturated. Exemplary heterocyclic groups include, but arenot limited to, aziridine, ethylene oxide (epoxides, oxiranes), thiirane(episulfides), dioxirane, azetidine, oxetane, thietane, dioxetane,dithietane, dithiete, azolidine, pyrrolidine, pyrroline, oxolane,dihydrofuran, and furan.

The term “polyol ester” refers to an ester of an organic compoundcontaining at least two hydroxyls with at least one carboxylic acid.

The term “surfactant” refers to a molecule having surface activity,including wetting agents, dispersants, emulsifiers, detergents, andfoaming agents, and the like. It is understood to be inclusive of theuse of a single surfactant or multiple surfactants.

The term “weight percent,” “wt. %,” “wt-%,” “percent by weight,” “% byweight,” and variations thereof, as used herein, refer to theconcentration of a substance as the weight of substance divided by thetotal weight of the composition and multiplied by 100.

As used herein, the term “free of a compound” refers to a composition,mixture, or ingredient does not contain the compound or to which thecompound has not been added. Should the compound be present throughcontamination of a composition, mixture, or ingredients free of thecompound, the amount of the compound shall be less than 0.5 wt %. Morepreferably, the amount of the compound is less than 0.1 wt-%, and mostpreferably, the amount of phosphate is less than 0.01 wt %. In thisdisclosure, the compound the disclosed grease composition is free of canbe a surfactant, additive, or combination thereof.

As used herein, the term “an existing grease composition” refers to agrease composition does not contain any functionalized carbonnanomaterial or boron nanomaterial. Such an existing grease compositioncan contain non-functionalized carbon nanomaterial.

The methods, systems, apparatuses, and compositions of the presentinvention may comprise, consist essentially of, or consist of thecomponents and ingredients of the present invention as well as otheringredients described herein. As used herein, “consisting essentiallyof” means the methods, systems, apparatuses and compositions may includeadditional steps, components or ingredients, but only if the additionalsteps, components or ingredients do not materially alter the basic andnovel characteristics of the claimed methods, systems, apparatuses, andcompositions.

Further terms are defined in the detailed description.

Conductive Grease Compositions

The conductive grease compositions comprise a fluid capable of hydrogenbonding and a nanomaterial. Preferred fluids capable of hydrogenbonding, include, a base oil capable of hydrogen bonding. Preferrednanomaterials are those functionalized having one or more of a firstfunctional group capable of forming an electrostatic attraction,including, but not limited to, a hydrogen bond or boron nanomaterial;and wherein the fluid comprises one or more of a second functional groupcapable of forming an electrostatic attraction, including, but notlimited to, a hydrogen bond with the first function group of thenanomaterial. Preferably, the conductive grease composition is stable.Preferably, the conductive grease is a nanogrease. Non-limiting,exemplary conductive grease compositions are shown the following table.

First Second Third Exemplary Exemplary Exemplary Composition CompositionComposition (wt. %) (wt. %) (wt. %) Fluid Component   25-99.9   50-99.575-95 Nanomaterial 0.1-20  0.5-10  0.5-5   Optional Additional  0-70 0-47  0-23 Components

The conductive grease compositions preferably have improved electricalconductivity and improved resistance. Preferably, the resistance isimproved (lowered) over the base oil alone by at least about 10%, 20%,30%, 40%, 50%, 60%, 70%, 80% when measured by the same test under thesame conditions. Preferably, the electrical conductivity is improved(increased) over the base oil alone by at least about 10%, 20%, 50%,100%, 200%, 250%, 300%, 400%, 500%, when measured by the same test underthe same conditions.

The conductive grease compositions preferably have improved thermalconductivity. Preferably, the thermal conductivity is improved(increased) over the base oil alone by at least about 10%, 20%, 30%,40%, 50%, 60%, 70% 80%, 90% 100%, 150%, 200%, 250%, 300%, 350%, whenmeasured by the same test under the same conditions.

The conductive grease compositions can optionally comprise one or moreadditional components added to provide properties to the grease. Forexample, such components can include grease additives, surfactants,viscosity modifiers, conductive particles, or combinations or mixturesthereof. Other additional components can also be added.

Fluid Component

In some embodiments, the base oil comprises an alkyl alcohol, alkyleneglycols, polyol ester, or a combination thereof. In some otherembodiments, the base oil comprises ethylene glycol or diethyleneglycol, a combination thereof. In yet some other embodiments, whereinthe base oil comprises a silicone transfer compound. In some otherembodiments, the base oil comprises glycerol.

In some embodiments, the grease composition further comprises water. Insome embodiments, the base oil is an existing grease composition. Insome other embodiments, the base oil is an existing commerciallyavailable common grease composition. In some embodiments, the base oilcomprises Valvoline Cerulean Grease, NYE grease, Krytox XHT 750, PAODurasyn 166, Petro-Canada NH650HT, or Royco 500.

In some embodiments, the composition comprises from about 25 wt-% toabout 99 wt-% of the base oil. In some other embodiments, thecomposition comprises from about 25 wt-% to about 90 wt-%, from about 25wt-% to about 85 wt-%, from about 25 wt-% to about 80 wt-%, from about25 wt-% to about 75 wt-%, from about 25 wt-% to about 70 wt-%, fromabout 25 wt-% to about 65 wt-%, from about 25 wt-% to about 60 wt-%,from about 25 wt-% to about 55 wt-%, from about 25 wt-% to about 50wt-%, from about 25 wt-% to about 45 wt-%, from about 25 wt-% to about40 wt-%, from about 25 wt-% to about 35 wt-%, from about 25 wt-% toabout 30 wt-%, from about 30 wt-% to about 99 wt-%, from about 35 wt-%to about 99 wt-%, from about 45 wt-% to about 99 wt-%, from about 55wt-% to about 99 wt-%, from about 65 wt-% to about 99 wt-%, from about75 wt-% to about 99 wt-%, from about 80 wt-% to about 99 wt-%, fromabout 85 wt-% to about 99 wt-%, from about 99 wt-% to about 99 wt-%,from about 25 wt-% to about 95 wt-%, from about 35 wt-% to about 95wt-%, from about 45 wt-% to about 95 wt-%, from about 55 wt-% to about95 wt-%, from about 65 wt-% to about 95 wt-%, from about 75 wt-% toabout 95 wt-%, from about 85 wt-% to about 95 wt-%, from about 25 wt-%to about 85 wt-%, from about 35 wt-% to about 75 wt-%, from about 45wt-% to about 65 wt-%, from about 55 wt-% to about 60 wt-%, about 25wt-%, about 35 wt-%, about 40 wt-%, about 45 wt-%, about 55 wt-%, about60 wt-%, about 65 wt-%, about 70 wt-%, about 75 wt-%, about 80 wt-%,about 85 wt-%, about 90 wt-%, about 95 wt-%, about 99 wt-%, or any valuetherebetween of the base oil.

In another aspect, the present disclosure is a method of enhancingthermal or electric conductivity and/or resistance of a greasecomposition, the method comprises adding into a grease composition ananomaterial to form an improved grease composition, wherein thenanomaterial is a functionalized carbon nanomaterial having one or moreof a first functional group capable of forming a an electrostaticattraction, including, but not limited to, a hydrogen bond with a secondfunctional group in the grease composition or boron nanomaterial.

In some other embodiments the method further comprising adding water ora base oil, wherein the base oil comprises a functional group capable offorming an electrostatic attraction, including, but not limited to, ahydrogen bond with the first functional group of the nanomaterial.

In some embodiments, the nanomaterial comprises a carbon nanomaterial,boron nanomaterial, or combination thereof. In some embodiments, thenanomaterial comprises a single- walled carbon, multiple-walled carbon,single-walled boron, multiple-walled boron nanomaterial, or combinationthereof. In some embodiments, the improved grease composition is one ofthe grease compositions disclosed herein.

Base Oil

A preferred fluid for use in the conductive grease compositions is abase oil. Suitable base oils are preferably capable of hydrogen bonding.A base oil may be selected from a wide variety of well-known organicoils, including petroleum distillates, synthetic petroleum oils,greases, gels, oil-soluble polymer composition, vegetable oils, andcombinations thereof. Petroleum distillates, also known as mineral oils,generally include paraffins, naphthenes and aromatics. Preferably, thebase oil can form hydrogen bonds or similar electrostatic attractions.The American Petroleum Institute (API) generally sorts base oils intofive groups, three of which are mineral oils and two of which aresynthetic: (1) solvent refined paraffinic mineral oils, (2) saturatedparaffinic mineral oils, (3) synthesized hydrocarbon paraffinic mineraloils, (4) polyalphaolefin (PAO) synthetic oils, and (5) non-PAOsynthetic oils.

Mineral Oils

Solvent refined paraffinic mineral oils (API Group I Oils), typicallyhave less than 90% saturates, greater than 0.03% sulfur, and aviscosity-index range of about 80 to about 120. The temperature rangefor these oils is from about 32 to about 150° F.

Saturated paraffinic mineral oils (API Group II Oils), sometimesreferred to as hydrotreated oils, also typically have greater than 90%saturates, less than 0.03% sulfur, and a viscosity-index range of about80 to about 120. These oils are often clearer than the solvent refinedparaffinic mineral oils.

Synthesized hydrocarbon paraffinic mineral oils (API Group III Oils),sometimes referred to as hydrocracked oils, typically have greater than90% saturates, less than 0.03% sulfur, and a viscosity-index greaterthan about 120.

Synthetic Oils

PAO synthetic oils (API Group IV Oils) are synthetic oils based onpolymers of an alpha olefin structure. They are suitable for use in abroad temperature range. PAO synthetic oils can be preferred for use invery cold conditions or in high-heat conditions.

Non-PAO oils (API Group V Oils) are synthetic oils not based on thealpha olefin structure. The most common non-PAO synthetic oils areester-based oils, however, other types are common too. For example,non-PAO synthetic oils include, but are not limited to, silicone oils,phosphate ester oils, hindered ester oils, polyalkylene glycol (PAG)oils, polyglycol oils, polyolester oils, water-glycol fluids, diesters(dibasic acid ester), biolubes, naphthenic oil, alkylated naphthalene(AN), polyether, phenyl ether polymer or polyphenyl ethers (PPEs),Polyvinyl ether (PVE), halogenated hydrocarbons, Fluids based onhalogenated (fluorinated and/or chlorinated) hydrocarbons includechlorofluorcarbons (CFC), halogenated fluorocarbons (HFC), halogenatedchlorofluorocarbon (HCFC), and perfluorocarbon (PFC) fluids, and othersynthetic fluids. Silicone base oils can include, but are not limitedto, fluorosilicones, alkylmethylsilicones, and other silicone-basedoils.

While the compositions of the invention can use a wide variety of oils,preferred base oils include synthetic oils. Preferred base oils for usein the compositions and methods include, but are not limited to,alkylaryls such as dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes,and di-(2-ethylhexyl)benzenes; polyphenyls such as biphenyls,terphenyls, and alkylated polyphenyls; fluorocarbons such aspolychlorotritluoroethylenes and copolymers of perfluoroethylene andperfluoropropylene; polymerized olefins such as polybutylenes,polypropylenes, propylene- isobutylene copolymers, chlorinatedpolybutylenes, poly(1-octenes), and poly(1-decenes); organic phosphatessuch as triaryl or trialkyl phosphates, tricresyl phosphate, trioctylphosphate, and diethyl ester of decylphosphonic acid; and silicates suchas tetra(2-ethylhexyl) silicate, tetra(2- ethylbutyl) silicate, andhexa(2-ethylbutoxy) disiloxane. Other examples include polyol esters,polyglycols, polyphenyl ethers, polymeric tetrahydrofurans, andsilicones.

In one embodiment of the present disclosure, the base oil is a diesterwhich is formed through the condensation of a dicarboxylic acid, such asadipic acid, azelaic acid, fumaric acid, maleic acid, phtalic acid,sebacic acid, suberic acid, and succinic acid, with a variety ofalcohols with both straight, cyclic, and branched chains, such as butylalcohol, dodecyl alcohol, ethylene glycol diethylene glycol monoether,2-ethylhexyl alcohol, isodecyl alcohol, hexyl alcohol, pentaerytheritol,propylene glycol, tridecyl alcohol, and trimethylolpropane. Modifieddicarboxylic acids, such as alkenyl malonic acids, alkyl succinic acids,and alkenyl succinic acids, can also be used. Specific examples of theseesters include dibutyl adipate, diisodecyl azelate, diisooctyl azelate,di-hexyl fumarate, dioctyl phthalate, didecyl phthalate,di(2-ethylhexyl) sebacate, dioctyl sebacate, dicicosyl sebacate, and the2-ethylhexyl diester of linoleic acid dimer, the complex ester formed byreacting one mole of sebacic acid with two moles of tetraethylene glycoland two moles of 2-ethylhexanoic acid.

In another embodiment, the base oil is a polyalphaoletin which is formedthrough oligomerization of 1-olefines containing 2 to 32 carbon atoms,or mixtures of such olefins. Some common alphaolefins are 1-octene,1-decene, and 1-dodecene. Examples of polyalphaolefins includepoly-1-octene, poly-1-decene, poly-1-dodecene, mixtures thereof, andmixed olefin-derived polyolefins. Polyalphaolefins are commerciallyavailable from various sources, including DURASYN® 162, 164, 166, 168,and 174 (BP-Amoco Chemicals, Naperville, Ill.), which have viscositiesof 6, 18, 32, 45, and 460 centistokes, respectively.

In yet another embodiment, the base oil is a polyol ester which isformed through the condensation of a monocarboxylic acid containing 5 to12 carbons and a polyol and a polyol ether such as neopentyl glycol,trimethylolpropane, pentaerythritol, dipentaerythritol, andtripentaerythritol. Examples of commercially available polyol esters areROYCO® 500, ROYCO® 555, and ROYCO® 808. ROYCO® 500 contains about 95% ofpentaerythritol esters of saturated straight fatty acids with 5 to 10carbons, about 2% of tricresyl phosphate, about 2% ofN-phenyl-alpha-naphthylamine, and about 1% of other minor additives.ROYCO® 808 are about 30 to 40% by weight of trimethylolpropane esters ofheptanoic, caprylic and capric acids, 20 to 40% by weight oftrimethylolpropane esters of valerie and heptanoic acids, about 30 to40% by weight of neopentyl glycol esters of fatty acids, and other minoradditives. Generally, polyol esters have good oxidation and hydrolyticstability. The polyol ester for use herein preferably has a pour pointof about −100° C. or lower to −40° C. and a viscosity of about 2 to 100centistoke at 100° C.

In yet another embodiment, the base is a polyglycol which is an akyleneoxide polymer or copolymer. The terminal hydroxyl groups of a polyglycolcan be further modified by esterification or etherification to generateanother class of known synthetic oils. Interestingly, mixtures ofpropylene and ethylene oxides in the polymerization process will producea water-soluble lubricant oil. Liquid or oil type polyglycols have lowerviscosities and molecular weights of about 400, whereas 3,000 molecularweight polyglycols are viscous polymers at room temperature.

In yet another embodiment, the base oil is a combination of two or moreselected from the group consisting of petroleum distillates, syntheticpetroleum oils, greases, gels, oil-soluble polymer composition, andvegetable oils. Suitable examples include, but not limited to, a mixtureof two polyalphaolefins, a mixture of two polyol esters, a mixture ofone polyalphaolefine and one polyol ester, a mixture of threepolyalphaolefins, a mixture of two polyalphaolefins and one polyolester, a mixture of one polyalphaolefin and two polyol esters, and amixture of three polyol esters. In all the embodiments, the base oilpreferably has a viscosity of from about 1 to about 1,000 centistokes,more preferably from about 2 to about 800 centistokes, and mostpreferably from about 5 to about 500 centistokes.

In yet another embodiment, the base oil is grease which is made bycombining a petroleum or synthetic lubricating fluid with a thickeningagent. The thickeners are generally silica gel and fatty acid soaps oflithium, calcium, strontium, sodium, aluminum, and barium. The greaseformulation may also include coated clays, such as bentonite andhectorite clays coated with quaternary ammonium compounds. Sometimescarbon black is added as a thickener to enhance high-temperatureproperties of petroleum and synthetic lubricant greases. The addition oforganic pigments and powders which include aryl urea compoundsindanthrene, ureides, and phthalocyanines provide high temperaturestability. Sometimes, solid powders such as graphite, molybdenumdisulfide, asbestos, talc, and zinc oxide are also added to provideboundary lubrication. Formulating the foregoing grease compositions withthickeners provides specialty greases. The synthetic lubricant oilsinclude, without limitation, diesters, polyalphaolefins, polyol esters,polyglycols, silicone-diester, and silicone lubricants. Non-meltingthickeners are especially preferred such as copper phthalocyanine,arylureas, indanthrene, and organic surfactant coated clays.

Nanomaterials

The conductive grease compositions comprise a nanomaterial. Preferrednanomaterials are those functionalized having one or more of a firstfunctional group capable of forming an electrostatic attraction,including, but not limited to, a hydrogen bond or boron nanomaterial;and wherein the fluid comprises one or more of a second functional groupcapable of forming an electrostatic attraction, including, but notlimited to, a hydrogen bond with the first function group of thenanomaterial. Preferred nanomaterials include, but are not limited to,carbon particles and boron nanomaterials.

In some embodiments, the first and second functional group is ahydrophilic functional group. In some other embodiments, the first andsecond function group are independently —OH, —NH, —COOH, —F, —BH, —O—,—N—, or combination thereof. In yet some other embodiments, the firstfunctional group is sulfonate, carboxyl, hydroxyl, amino, amide, urea,carbamate, urethane, or phosphate and the second functional group is—OH, —NH, —COOH, —F, —BH, —O—, —N—, or combination thereof. In someembodiments, the base oil comprises at least one compound have at leastone functional group can form an electrostatic attraction, including,but not limited to, a hydrogen bond with at least one functional groupin a functionalized carbon nanomaterial or boron nanomaterial.

In some embodiments, the nanomaterial is carbon nanomaterial. In someother embodiments, the nanomaterial is carbon nanotube. In someembodiments, the nanomaterial is a single-walled, multiple-wallednanotube, or a mixture thereof. In some other embodiments, thenanomaterial is a OH functionalized carbon nanomaterial. In yet someother embodiments, the nanomaterial is a fluorine functionalized carbonnanomaterial.

In some embodiments, the nanomaterial is a OH functionalized carbonmulti-walled nanotube. In some other embodiments, the nanomaterial is afluorine functionalized carbon multi- walled nanotube. In yet some otherembodiments, the nanomaterial is a OH functionalized carbonsingle-walled nanotube. In some other embodiments, the nanomaterial is afluorine functionalized carbon single-walled nanotube.

In some embodiments, the nanomaterial is boron nanomaterial. In someother embodiments, the nanomaterial is a single-walled boron nanotube.In yet some other embodiments, the nanomaterial is a multiple-walledboron nanotube.

In some embodiments, the nanomaterial comprises both carbon and boronnanomaterial. In some other embodiments, wherein the nanomaterialcomprises both carbon and boron nanotubes. In some other embodiments,the nanomaterial comprises single-walled carbon, multiple-walled carbon,single-walled boron, multiple-walled boron nanotube, or a combinationthereof.

In some embodiments, the improved grease composition comprises fromabout 0.1 wt-% to about 20 wt-% of the nanomaterial, more preferablybetween about 0.5 wt % and about 10 wt. %, still more preferably fromabout 0.1 wt-% to about 5-% of the nanomaterial. In some otherembodiments, wherein the composition comprises from about 0.5 wt-% toabout 3 wt-% of the nanomaterial. In yet some other embodiments, thecomposition comprises from about 0.5 wt-% to about 2 wt-% of thenanomaterial. In some other embodiments, the composition comprises fromabout 0.5 wt-% to about 1.5 wt-% of the nanomaterial. An advantage ofthe conductive greases described herein is greases can be prepared withless carbon loading than previously done while maintaining or improvingthe thermal and/or electrical properties. This provides a cost reductionin addition to conductivity improvement.

Carbon Particles and Boron Nanomaterials

The conductive grease compositions and methods of making the samecomprise carbon particles and/or boron nanomaterials. The carbonparticles are preferably nanoparticles or nanomaterials. As used hereinthe reference to nanoparticles or nanomaterials (carbon or boron)includes particles or materials having at least one dimension is lessthan 10,000 nanometers. Preferably, the nanoparticles and/ornanomaterials have at least one dimension less than 5000 nanometers,more preferably 1000 nanometers, still more preferably less than 750nanometers, even more preferably less than 500 nanometers, and mostpreferably less than 250 nanometers. The terms “nanoparticle” and“nanomaterial” include, for example “nanospheres,” “nanorods,”“nanocups,” “nanowires,” “nanoclusters,” “nanofibers,” “nanolayers,”“nanotubes,” “nanocrystals,” “nanobeads,” “nanobelts,” and “nanodisks.”

The terms “carbon nanoparticle” and “carbon nanomaterial” refer to ananoparticle or nanomaterial which contain primarily carbon element,including, but not limited to, diamond, graphite, fullerenes, carbonnanotubes, carbon fibers, and combinations thereof. Similarly, the terms“boron nanoparticle” and “boron nanomaterial” refers to a nanoparticleor nanomaterial which primarily contain boron element or boroncompounds.

The term “nanotube” refers to a class of nanoparticle or nanomaterialwhich have a shape of a long thin cylinder and contain primarily carbonelement. The term “aspect ratio” refers to a ratio of the length overthe diameter of a particle. The term “SWNT” refers to a single-wallednanotube. The term “MWNT” refers to a multi-walled nanotube. The term“D-WNT” refers to a double-walled nanotube. The term “F-SWNT” refers toa fluorinated SWNT.

Similarly, the term “carbon nanotube” refers to a class of carbonnanoparticle which have a shape of a long thin cylinder and containprimarily carbon element. The term “boron nanotube” refers to a class ofboron nanoparticle which have a shape of a long thin cylinder andcontain primarily carbon element. Both carbon and boron nanotube can bemulti-wall or single walled nanotube.

Carbon nanotubes (“CNT”) are nanoparticles in the shape of a long thincylinder often with a diameter in few nanometers. The basic structuralelement in a carbon nanotube is a hexagon which is the same as found ingraphite. Based on the orientation of the tube axis with respect to thehexagonal lattice, a carbon nanotube can have three differentconfigurations: armchair, zigzag, and chiral (also known as spiral). Inarmchair configuration, the tube axis is perpendicular to two of sixcarbon-carbon bonds of the hexagonal lattice. In zigzag configuration,the tube axis is parallel to two of six carbon-carbon bonds of thehexagonal lattice. Both these two configurations are achiral. In chiralconfiguration, the tube axis forms an angle other than 90 or 180 degreeswith any of six carbon-carbon bonds of the hexagonal lattice.

Carbon nanotubes of these configurations often exhibit differentphysical and chemical properties. For example, an armchair nanotube isalways metallic whereas a zigzag nanotube can be metallic orsemi-conductive depending on the diameter of the nanotube. All threedifferent nanotubes are expected to be very good thermal conductorsalong the tube axis, exhibiting a property known as “ballisticconduction,” but good insulators laterally to the tube axis.

In addition to the common hexagonal structure, the cylinder of a carbonnanotube molecule can also contain other size rings, such as pentagonand heptagon. Replacement of some regular hexagons with pentagons and/orheptagons can cause cylinders to bend, twist, or change diameter, andthus lead to some interesting structures such as “Y-,” “T-,” and“X-junctions,” and different chemical activities. Those variousstructural variations and configurations can be found in both SWNT andMWNT. However, the present invention is not limited by any configurationand structural variation. The carbon nanotube used in the presentinvention can be in the configuration of armchair, zigzag, chiral, orcombinations thereof. The carbon nanotube can also contain structuralelements other than hexagon, such as pentagon, heptagon, octagon, orcombinations thereof.

Another structural variation for MWNT molecules is the arrangement ofthe multiple tubes. A perfect MWNT is like a stack of graphene sheetsrolled up into concentric cylinders with each wall parallel to thecentral axis. However, the tubes can also be arranged so an anglebetween the graphite basal planes and the tube axis is formed. Such MWNTis known as a stacked cone, Chevron, bamboo, ice cream cone, or piledcone structures. A stacked cone MWNT can reach a diameter of about 1 00nm. Despite these structural variations, all MWNTs are suitable for thepresent invention if they have an excellent thermal conductivity. Theterm MWNT used herein also includes double-walled nanotubes (“D-WNT”).

In some embodiments, the carbon nanotubes are single-walled nanotubes(“SWNT”), double-walled nanotubes (“DWNT”), multi-walled nanotubes(“MWNT”), or a combination of the same. In some other embodiment, thecarbon nanotubes include carbon SWNT, MWNT, and/or DWNT. As used herein,the term MWNT is inclusive of DWNTs.

In some embodiments, the boron nanotubes are single-walled nanotubes(“SWNT”), double-walled nanotubes (“DWNT”), multi-walled nanotubes(“MWNT”), or a combination of the same. In some other embodiment, theboron nanotubes include boron SWNT, MWNT, and/or DWNT.

Carbon or boron nanotubes used in the present invention can alsoencapsulate other elements and/or molecules within their enclosedtubular structures. Such elements include Si, Ti, V, Cr, Mn, Fe, Co, Ni,Cu, Y, Zr, Mo, Ta, Au, Th, La, Ce, Pr, Nb, Gd, Tb, Dy, Ho, Er, Tm, Yb,Lu, Mo, Pd, Sn, and W. Carbon nanotubes used in the present disclosurealso include alloys of these elements such as alloys of cobalt with S,Br, Pb, Pt, Y, Cu, B, and Mg, and compounds such as the carbides (i.e.TiC, MoC, etc.) The present of these elements, alloys and compoundswithin the core structure of fullerenes and nanotubes can enhance thethermal conductivity of these nanotubes which then translates to ahigher thermal conductive nanofluid when these nanotubes are suspend ina heat transfer fluid.

Carbon nanotubes used in the present invention can also be chemicallymodified and functionalized to be so-called “functionalized carbonnanotubes”, such as covalently attached hydrophilic groups to increasetheir solubility in hydrophilic fluids or lipophilic chains to increasetheir solubility in hydrophobic oils. Covalent functionalization ofcarbon nanotubes, especially fullerenes, has commonly been accomplishedby three different approaches, namely, thermally activated chemistry,electrochemical modification, and photochemical functionalization. Themost common methods of thermally activated chemical functionalizationare addition reactions on the sidewalls. For example, the extensivetreatment of a nanotube with concentrated nitric and sulfuric acidsleads to the oxidative opening of the tube caps as well as the formationof holes in the sidewalls and thus produces a nanotube decorated withcarboxyl groups, which can be further modified through the creation ofamide and ester bonds to generate a vast variety of functional groups.

The carbon nanotube can also be modified through addition reactions withvarious chemical reagents such halogens and ozone. Unlike thermallycontrolled modification, electrochemical modification of carbonnanotubes can be carried out in more selective and controlled manner.Interestingly, a SWNT can be selectively modified or functionalizedeither on the cylinder sidewall or the optional end caps. These twodistinct structural moieties often display different chemical andphysical characteristics. The functional group on functionalized carbonnanotubes may be attached directly to the carbon atoms of a carbonnanotubes or via chemical linkers, such as alkylene or arylene groups.To increase hydrophilicity, carbon nanotubes can be functionalized withone or more hydrophilic functional groups, such as, sulfonate, carboxyl,hydroxyl, amino, amide, urea, carbamate, urethane, and phosphate. Toincrease hydrophobicity, carbon nanoparticles may be functionalized withone or more hydrophobic alkyl or aryl groups. The functionalized carbonnanoparticle may have no less than about 2, no less than about 5, noless than about 10, no less than about 20, or no less than about 50functional groups on average.

The term “carbon nanotube” or “boron nanotube” used herein refers to allstructural variations and modification of SWNT and MWNT discussedhereinabove, including configurations, structural defeats andvariations, tube arrangements, chemical modification andfunctionalization, and encapsulation.

To some extent, any carbon nanomaterial can be chemically modified orfunctionalized to become a “functionalized carbon nanomaterial”, in asimilar way for carbon nanotubes.

Carbon nanotubes are commercially available from a variety of sources.Single walled carbon nanotubes can be obtained from Carbolex (Broomall,Pa.), MER Corporation (Tucson, Ariz.), and Carbon NanotechnologiesIncorporation (“CNI”, Houston, Tex.). Multi-walled carbon nanotubes canbe obtained from MER Corporation (Tucson, Ariz.) and Helix materialsolution (Richardson, Tex.). However, the present invention is notlimited by the source of carbon nanotubes. In addition, manypublications are available with enough information to allow one tomanufacture nanotubes with desired structures and properties. The mostcommon techniques are arc discharge, laser ablation, chemical vapordeposition, and flame synthesis. In general, the chemical vapordeposition has shown the most promise in being able to produce largerquantities of nanotubes at lower cost. This is usually done by reactinga carbon containing gas, such as acetylene, ethylene, ethanol, etc.,with a metal catalyst particle, such as cobalt, nickel, or ion, attemperatures above 600° C.

The selection of a carbon nanomaterial depends on several factors. Themost important factor is the carbon nanomaterial is a functionalizedcarbon nanomaterial having one or more functional groups forming ahydrogen bond with another functional group existing in an alreadyexisting base oil or just co-existing base oil. Boron nanomaterial cangenerally form hydrogen bond with another functional group capable offorming hydrogen bond.

Another important consideration is the nanomaterial must be compatiblewith an already existing base oil discussed thereafter. Other factorsinclude heat transfer properties, electrical transfer properties, costeffectiveness, solubility, dispersion and settling characteristics. Insome embodiments of the present disclosure, the carbon nanomaterialselected contain predominantly single-walled functionalized carbonnanotubes. In some other embodiments, the nanomaterial selected containpredominantly multi-walled functionalized carbon nanotubes. In someembodiments of the present disclosure, the carbon nanomaterial selectedcontain predominantly single-walled boron nanotubes. In some otherembodiments, the nanomaterial selected contain predominantlymulti-walled boron nanotubes.

In one aspect, the carbon nanotube has a carbon content of no less thanabout 60%, no less than about 80%, no less than about 90%, no less thanabout 95%, no less than about 98%, or no less than about 99%.

In another aspect, the carbon or boron nanotube has a diameter of fromabout 0.2 to about 100 nm, from about 0.4 to about 80 nm, from about 0.5to about 60 nm, or from about 0.5 to about 50 nm. In yet another aspect,the carbon nanotube is no greater than about 200 micrometers, no greaterthan 100 micrometers, no greater than about 50 micrometers, or nogreater than 20 micrometers in length. In yet another aspect, the carbonnanotube has an aspect ratio of not greater than 1,000,000, no greaterthan 100,000, no greater than 10,000, no greater than 1,000, no greaterthan about 500, no greater than about 200, or no greater than about 100.

Grease Additives

In some embodiments, the conductive grease compositions further comprisea grease additive. In some other embodiments, the composition furthercomprises MoS₂ as an additive. In some other embodiments, the conductivegrease composition is free of other grease additive.

Surfactants

The conductive grease compositions can include a surfactant or be freeof surfactant. Surfactants suitable for use with the compositions of thepresent invention include, but are not limited to, nonionic surfactants,anionic surfactants, and zwitterionic surfactants. In some embodiments,the compositions of the present invention include about 10 wt % to about50 wt % of a surfactant. In other embodiments the compositions of thepresent invention include about 15 wt % to about 30% of a surfactant. Instill yet other embodiments, the compositions of the present inventioninclude about 25 wt % of a surfactant. In some embodiments, thecompositions of the present invention include about 100 ppm to about1000 ppm of a surfactant.

Viscosity Modifiers

The conductive grease compositions can optionally comprise a viscositymodifier. Preferred viscosity modifiers include thickeners.

Methods of Preparing the Conductive Grease Compositions

The conductive grease compositions can be prepared with a variety ofequipment and under conditions specific to the ingredients for theconductive grease composition. For example, the method may includeheating the fluid, such carbon particles and/or boron nanomaterials canbe dispersed therein. The precise temperature of the heating may bedictated by the melting point or boiling point of the fluid.

The conductive grease compositions can be prepared in batch orcontinuous processes. To prepare the conductive grease compositions, thefluid may be heated. Preferably, the fluid is heated. The temperature ofheating may vary based on the fluid. Preferably it is a temperaturebetween about 60° C. and about 200° C., more preferably a temperaturebetween about 70° C. and about 180° C. In some embodiments, heating isnot necessary. For example, in an embodiment where water is the fluid orcomprises a significant percentage of the fluid, heating is notrequired.

After heating the base oil, carbon particles and/or boron nanomaterialscan be added to the base oil. The carbon particles and/or boronnanomaterials can be added all at once or sequentially in smallerportions. Preferably, the carbon particles and/or boron nanomaterialsare mixed or stirred in the fluid to form a conductive greasecomposition. If the carbon particles and/or boron nanomaterials areadded sequentially in small portions, the mixing and/or stirring can beperformed as the nanotubes are being added and/or between sequentialadditions. Preferred mixing and stirring methods, include, but are notlimited to, automatic mixers (such as paddle mixers), stir bars, manualstirring or manual mixing, sonication, etc. The intensity and speed ofthe mixing or stirring can vary. Preferably, the intensity and/or speedare not too vigorous to break or degrade the carbon particle and/orboron nanomaterial structures. The stirring can occur for any amount oftime enough to disperse the carbon particles and/or boron nanomaterials.Preferably, the carbon particles and/or boron nanomaterials arethoroughly dispersed; most preferably, the carbon particles and/or boronnanomaterials are homogenously dispersed in the fluid. Preferred mixingand/or stirring times can be between about 1 minute and 2 hours; morepreferably, between about 2 minutes and about 1 hour; most preferablybetween 5 minutes and 30 minutes. In an embodiment where the preparationof the conductive grease compositions is a continuous process, themixing may be continuous.

After mixing, the conductive grease composition can optionally beheated, cooled, or maintained at the same temperature. If the conductivegrease composition is heated, it is preferably heated to a temperaturebetween about 80° C. and about 240° C., more preferably to a temperaturebetween about 100° C. and about 220° C. The heating can be performed fora time between about 1 minute and about 2 hours; more preferably betweenabout 5 minutes and about 90 minutes; most preferably between about 10minutes and about 1 hour.

Preferably the conductive grease is passed through a roller mill, anextruder, a manual or mechanical stirrer. Preferably, the conductivegrease is passed through a roller mill. Preferred roller mills include,but are not limited to, two-roll mills and three-roll mills. Preferablythe conductive grease composition is passed through a roller mill enoughtimes to obtain a smooth consistency. In a preferred method, theconductive grease is passed through a roller mill between 1 and 20times, more preferably between 2 and 15 times, most preferably between 3and 10 times. The conductive grease can be passed through the sameroller mill multiple times or through a series of roller mills toachieve the desired number of pass-throughs.

After passing the conductive grease through a roller mill, theconductive grease can be heated, cooled, or maintained at the sametemperature.

While an understanding of the mechanism is not necessary to practice thepresent invention and while the present invention is not limited to anymechanism of action, it is contemplated the combination of a fluid andnanomaterial can form an electrostatic attraction, including, but notlimited to, a hydrogen bond among them leads to enhanced thermal andelectrical conductivity. Because of this combination, the disclosedgrease compositions herein possess an enhanced thermal and/or electricalconductivity. The disclosed grease compositions are also more stableeven under tough conditions.

All publications and patent applications in this specification areindicative of the level of ordinary skill in the art to which thisinvention pertains. All publications and patent applications are hereinincorporated by reference to the same extent as if each individualpublication or patent application was specifically and individuallyindicated as incorporated by reference.

EXAMPLES

Embodiments of the present invention are further defined in thefollowing non-limiting Examples. These Examples, while indicatingcertain embodiments of the invention, are given by way of illustrationonly. From the above discussion and these Examples, one skilled in theart can ascertain the essential characteristics of this invention, andwithout departing from the spirit and scope thereof, can make variouschanges and modifications of the embodiments of the invention to adaptit to various usages and conditions. Thus, various modifications of theembodiments of the invention, in addition to those shown and describedherein, will be apparent to those skilled in the art from the foregoingdescription. Such modifications are also intended to fall within thescope of the appended claims.

Example 1

In this Example, a series of greases by three roll mills and theirresistances were measured, respectively.

An exemplary procedure to make a grease is following. First, heat 92.5 gN650HT Oil to 120° C. on a hot plate; slowly add 7.5 g multi wall carbonnanotubes (MWNT-OH Industrial Grade) while stirring at a speed settingof 3 of hot plate. Once all carbon nanotubes have been added, continueto stir for 10 minutes. Then, raise temperature to 150° C. whilestirring for 30 minutes at 150° C. Afterwards, allow the product to cooldown while stirring until it is safe to handle. Finally, manufacture thegrease through the three-roll mill 8-times to obtain a smoothconsistency grease. FIG. 1 shows the grease based on 7.5 wt %MWNT-OH/92.5 wt % Ester oil. FIG. 2 shows a SEM image of the greasebased on 7.5 wt % MWNT-OH/92.5 wt % Ester oil. This image clearlyindicates nanotubes form a network is contributing the conductivity.

Table 1 lists the ingredients and the measured resistances. Theresistance was measured with a Keithly instrument 2401.

TABLE 1 The ingredients and measured resistance of some exemplarygreases. Resistance Base Oil Carbon Material Carbon wt. % (ohm · cm)Petro-Canada NH650HT MWNT-OH 7.5 22.4 (Industrial) ROYCO 500 MWNT-OH 7.580 (Industrial) PAO Durasyn 166 MWNT-OH 7.5 4.5k (Industrial)Petro-Canada NH650HT Nano C SWNT 2 2.3k Petro-Canada NH650HT CNT-MWCNT8.4 7.88k Krytox XHT750 Helix MWNT 15 40 Krytox XHT750 MWNT-OH 1.8 18.6(Industrial) Ethylene Glycol MWNT-OH 4.46 96 (Industrial) EthyleneGlycol MWNT (Industrial) 12.53 46 Glycerol MWNT-OH 4.5 28 (Industrial)Glycerol MWNT (Industrial) 12.5 48.5 75% Glycerol/25% Water MWNT-OH 4.510 (Industrial) 50% Glycerol/50% Water MWNT-OH 4.5 20 (Industrial) 50%Glycerol/(25% Water/25% MWNT-OH 4.5 16.83 EG) (Industrial) 50% EthyleneMWNT-OH 5.68 11.9 Glycol/50% Water (Industrial) PAO Durasyn 166 HelixMWNT 20 2.7k Petro-Canada NH650HT Pyrograf Pr-19-XT- 10 16.1k HHT PAODurasyn 166 Pyrograf Pr-19-XT- 12 227 HHT Glycerol Pyrograf Pr-19-XT- 12175 HHT PAO Durasyn 166 Pyrograf Pr-19-XT- 4.48 each 138 HHT CNF andMWNT-OH (Industrial) 50% Glycerol/50% Water MWNT-OH 4.5 (10% NaCl 130(Industrial) Added) Glycerol MWNT-OH 4.5 (3% Cu 178 (Industrial)Nanoparticles added) Commercial grease Nyogel unknown unknown 300-500758G

All greases made were found to be stable. No oil leaks were found forthese grease samples for at least 10 days after they were applied to atest device. The stability of the grease compositions was assessedvisually. If unstable the oil will separate and collect on top of thegrease. This was not observed for any of the exemplary samples preparedand examined.

As shown in Table 1, some greases are better than the common commercialgrease in terms of electrical resistances. Some samples show 4-5 timesconductivity enhancement. Closer study of the measured resistance valuesleads to an unexpected observation, is, the combination of a carbonnanotubes and base oil have functional groups for forming the hydrogenboding between them leads to a high conductivity grease. In other words,hydrogen bonding between a carbon nanotube and base oil is the reason tohave extra high conductivity.

For examples, the highest conductivity sample is 75% Glycerol/25% Waterwith MWNT-OH (4.5 wt % ), in which water or glycerol can form hydrogenbonds with MWNT-OH, OH functionalized multiple wall nanotubes. On theother hand, the lowest conductivity grease is Petro-Canada NH650HT withMWNT (8.4 wt % ) and fiber (10 wt %), in which no hydrogen bond ispossible between the MWNT and base oil. Predictably, oil has stronghydrogen bonding capability (krytox XHT750) leads to a very low nanotubeloading (<2 wt % ) and yet high conductivity.

Example 2

In this Example, friction coefficients of some exemplary greases weremeasured. FIG. 24A-FIG. 24D show the friction coefficients exhibited byCNT-based greases and three other conventional lubricant greases,Li-based grease, Ca-based grease, and Li-based greases with MoS₂ asadditive, in steady-state and fretting/oscillating motion condition aswell.

As shown in FIG. 24A-24D, in nearly all test conditions, CNT or CNT+MoS2based greases provided the lowest friction coefficients. The testing inFIG. 3C is representative of difficult conditions consistent with toughindustrial operations thermal greases may be exposed to), CNT- basedgreases achieved friction reduction by more than 50%. These results arealso unexpected.

In summary, comparing to the current commercial electrically conductivegrease which are made by mixing commercial Li grease and carbonparticles, the grease disclosed herein show unexpected betterconductivity, long stability, reduced friction coefficient.

The unexpected results in this disclosure also lead to an improved wayto significantly enhance the electrical conductivity of greases whilereduce the nanotube loading percentage. The new discovery here ishydrogen bonding between nanotube and oil is the key element for a goodconductivity performance. This discovery is totally different with theprior art, in which non- functional nanotubes in high percentages wereused for greases with higher thermal conductive, instead of electricalconductivity.

The sole thickener of carbon nanotubes in our grease structure makes ourgrease unique and valuable. Compared to commercial grease carbon isadded without bonding and conductivity decreased with the time, theconductivity of our grease shall keep stable.

Example 3

In this Example, the ability of the greases disclosed herein to increasethermal conductivity of some common high thermal conductivity greases.High thermal conductive grease was usually made by nanomaterial, such ascarbon and boron nanomaterial, and base oils. It was discoveredunexpectedly adding both water, oil/nanomaterials have functional groupsfor forming the hydrogen bonds between them can increase greases'thermal conductivity as well. In other words, hydrogen bonding is thekey to have extra high thermal conductivity in a grease, like have extraelectrical conductivity. It was also found out boron nanotube functionsimilarly to increase thermal conductivity as carbon nanotubes. Boronnanomaterial can form the hydrogen bonding as well.

The most unexpected results are a few percentages of the greasesdisclosed herein or nanomaterial can form hydrogen bond with anotherfunctional group existing in a commercial grease, the thermalconductivity of the commercial grease enhance significantly. Table 2shows the results of adding various hydrogen bond forming water, ornanomaterials into a base oil or greases. For example, 1 wt % loadingcould lead to 50 percent TC enhancement and 2-3 wt % loading lead tomore than 100% TC enhancement.

TABLE 2 Thermal Conductivities Enhancement of adding carbon or boronnanomaterial to grease compositions. TC 2nd Base TC Percent Base FluidFluid 1st particles 2nd particles (W/mK) Increase 17.2 g Glycerol N/A BNnano N/A 0.4584   47% 2.8 g (14%) 17.2 g PAO N/A BN nano N/A 0.2320 36.6% 2.8 g (14%) 14.3 g Fromblin N/A BN nano N/A 0.1562 44.50% #40001.3796 (8.78%) Glycerol 8.6 g (43%) Water BN-nano N/A 0.6528  45.8% 8.6g 2.8 g (14%) (43%) 17.2 g Glycerol N/A BN-nano CNF-19 1.4 g 1.4453  366% 1.4 g (7%) (7%) 17.2 g N/A CNF-19 0.7 g BN nano 2.1 g 0.8975  188% Glycerol 25% (3.5%) 75% (10.5%) 14 g Krytox XHT 750 N/A BN nanoN/A 0.1487  31.5% 1.0 g (9.1%) Glycerol 8.6 g (43%) Water BN-nano CNF-191.4 g 1.7885 299.5% 8.6 g 1.4 g (7%) (7%) (43%) 17.2 g Used Silicon N/ABN nano N/A 0.2618   44% oil from water bath 2.8 g (14%) heater 23.87 gUsed Silicon N/A CNF-19 N/A 0.5097 180.5% oil from water bath 1.24 g(4.9%) heater Used Silicon oil from N/A Silica nano N/A 0.1968    8%water bath heater 1.23 g (5.1%) Used 18.6 g Silicon N/A MWNT-OH N/A0.3390  86.6% oil from water bath 1.4 g (7%) heater NYE 758G grease N/ACNF-19 N/A 0.4781 163.3 (5%) 10 g Valvoline N/A CNF-19 N/A 0.3479 108.7%Cerulean Grease 0.38 g (3.66%) 5 g Glycerol (25%) 15 g H2O CNF-19 1.4 gN/A 1.9487 261.5% (75%) (6.54%) Old Grease Sample N/A CNF-19 N/A 0.5027 98.9% 9-1 (PAO with (5%) SWNT or MWNT) 5.0453 g (Apr. 6, 2017 1.0513 gfinal is N/A 0.48662 N/A 6% CNF-19 94% NYE 4.97% CNF- NYE 758G blank758G 19 grease) grease 10 g Valvoline N/A CNF-19 Graphene nano 0.2136  28% Cerulean Grease 0.19 g platelets 0.19 g (1.83%) (1.83%) 10 gValvoline N/A CNF-19 BN nano 0.19 g 0.2295  37.7% Cerulean Grease 0.19 g(1.83%) (1.83%) 5 g (Feb. 15, 2017 7.5% N/A CNF-19 N/A 0.6704 109.6%MWNT-OH 92.5% 0.265 g (5%) PAO 166) 5 g (MG Chemicals N/A CNF-19 N/A1.6995 143.4% Silicone Heat 0.265 g (5%) Transfer Compound) 5 g (MGChemicals N/A CNF-19 N/A 1.333   91% Silicone Heat 0.155 g (3%) TransferCompound) 5 g (MG Chemicals N/A CNF-19 N/A 0.9871  41.4% Silicone Heat0.051 g (1%) Transfer Compound)

The thermal conductivity data was obtained using the Hot Disk™ thermalconstants analyzer, using the following parameters:

measurement depth: 6 mm

room temperature: 25° C.

power: 0.025 W

measurement time: 16 seconds

sensor radius: 2.001 mm

TCR: 0.0471/K,

disk type: Kapton

temperature drift rec: yes

As can be seen in Table 2, the grease compositions prepared according tothe methods of the invention, having carbon particles or boronnanomaterials, had improved thermal conductivity values often of atleast 40% and even over 100%. Further, the Table demonstrates conductivegreases prepared with boron nanomaterials also provide improved thermalproperties.

There is an increasing interest in the development of conductivecoatings. Conductive coatings have a wide variety of applicability. Forexample, conductive coatings can be used for lightening shielding inaircraft or to prevent the buildup of a static charge on containershandling explosive materials. Others have sought to address theseissues. For example, U.S. Pat. No. 5,498,372 to Winston L. Hedgesdisclosed an electrically conductive polymeric composition for coatingvolatile chemical containers. However, Hedges' disclosure suffered fromproblems with the components agglomerating. U.S. Published PatentApplication Number 2011/0014356 to Fornes et al. provides anotherexample disclosing a complex layered material for covering a substrateto protect from lightning strikes. However, this material containstwelve layers of varying materials, including multiple layers of carbonplies. Not only is the material complex to prepare, but expensive interms of time and components. There is need for improved conductivecoating materials.

Accordingly, it is an objective of the present disclosure to provideconductive coating materials with enhanced electrical, thermal, and/orsemiconducting properties.

A further object of the invention is to provide conductive coatingmaterials are flexible and can be employed to a variety of surfaces.

Other objects, advantages and features of the present invention willbecome apparent from the following specification taken in conjunctionwith the accompanying figures.

FIGS. 25A and 25B show photographs of an exemplary conductive flexiblecoating composition comprising carbon nanomaterial and providingenhanced conductor/semiconductor properties on a surface.

While multiple embodiments are disclosed, still other embodiments of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the invention. Accordingly, the figures anddetailed description are to be regarded as illustrative in nature andnot restrictive. Figures represented herein are not limitations to thevarious embodiments according to the invention and are presented forexemplary illustration of the invention.

The present invention relates to conductive coating compositionscomprising a fluid capable of hydrogen bonding and a nanomaterial. Theconductive coatings have many advantages over existing conductivecoatings. For example, the conductive coatings have significantlyenhanced electrical, thermal, and/or semiconducting properties.Furthermore, the conductive coating compositions are flexible and can beapplied to a variety of surfaces.

Definitions

So, the present invention may be more readily understood, certain termsare first defined. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as commonlyunderstood by one of ordinary skill in the art to which embodiments ofthe invention pertain. Many methods and materials similar, modified, orequivalent to those described herein can be used in the practice of theembodiments of the present invention without undue experimentation, thepreferred materials and methods are described herein. In describing andclaiming the embodiments of the present invention, the followingterminology will be used in accordance with the definitions set outbelow. Moreover, the embodiments of this invention are not limited toelectrically conductive coating applications, which can vary and areunderstood by skilled artisans. It is further to be understood allterminology used herein is for the purpose of describing embodimentsonly and is not intended to be limiting in any manner or scope.

As used in this specification and the appended claims, the singularforms “a,” “an” and “the” can include plural referents unless thecontent clearly indicates otherwise. Further, all units, prefixes, andsymbols may be denoted in its SI accepted form.

Numeric ranges recited within the specification are inclusive of thenumbers defining the range and include each integer within the definedrange. Throughout this disclosure, various aspects of this invention arepresented in a range format. The description in range format is merelyfor convenience and brevity and should not be construed as an inflexiblelimitation on the scope of the invention. Accordingly, the descriptionof a range should be considered to have specifically disclosed all thepossible sub-ranges, fractions, and individual numerical values withinrange. For example, description of a range such as from 1 to 6 should beconsidered to have specifically disclosed sub-ranges such as from 1 to3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc.,as well as individual numbers within range, for example, 1, 2, 3, 4, 5,and 6, and decimals and fractions, for example, 1.2, 3.8, 1½, and 4¾This applies regardless of the breadth of the range.

The term “about,” as used herein, refers to variation in the numericalquantity can occur, for example, through typical measuring techniquesand equipment, with respect to any quantifiable variable, including, butnot limited to, mass, volume, time, distance, wave length, frequency,voltage, current, and electromagnetic field. Further, given solid andliquid handling procedures used in the real world, there is certainerror and variation is likely through differences in the manufacture,source, or purity of the ingredients used to make the compositions orcarry out the methods and the like. The term “about” also encompassesthese variations. Whether or not modified by the term “about,” theclaims include equivalents to the quantities.

The methods and compositions of the present invention may comprise,consist essentially of, or consist of the components and ingredients ofthe present invention as well as other ingredients described herein. Asused herein, “consisting essentially of” means the methods, systems,apparatuses and compositions may include additional steps, components oringredients, but only if the additional steps, components or ingredientsdo not materially alter the basic and novel characteristics of theclaimed methods, systems, apparatuses, and compositions.

As used herein, the term “alkyl” or “alkyl groups” refers to saturatedhydrocarbons having one or more carbon atoms, including straight-chainalkyl groups (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,octyl, nonyl, decyl, etc.), cyclic alkyl groups (or “cycloalkyl” or“alicyclic” or “carbocyclic” groups) (e.g., cyclopropyl, cyclopentyl,cyclohexyl, cycloheptyl, cyclooctyl, etc.), branched-chain alkyl groups(e.g., isopropyl, tert-butyl, sec-butyl, isobutyl, etc.), and alkyl-substituted alkyl groups (e.g., alkyl-substituted cycloalkyl groups andcycloalkyl-substituted alkyl groups).

Unless otherwise specified, the term “alkyl” includes both“unsubstituted alkyls” and “substituted alkyls.” As used herein, theterm “substituted alkyls” refers to alkyl groups having substituentsreplacing one or more hydrogens on one or more carbons of thehydrocarbon backbone. Such substituents may include, for example,alkenyl, alkynyl, halogeno, hydroxyl, alkylcarbonyloxy, arylcarbonyloxy,alkoxycarbonyloxy, aryloxy, aryloxycarbonyloxy, carboxylate,alkylcarbonyl, arylcarbonyl, alkoxycarbonyl, aminocarbonyl,alkylaminocarbonyl, dialkylaminocarbonyl, alkylthiocarbonyl, alkoxyl,phosphate, phosphonato, phosphinato, cyano, amino (including alkylamino, dialkylamino, arylamino, diarylamino, and alkylarylamino),acylamino (including alkylcarbonylamino, arylcarbonylamino, carbamoyland ureido), imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate,sulfates, alkylsulfinyl, sulfonates, sulfamoyl, sulfonamido, nitro,trifluoromethyl, cyano, azido, heterocyclic, alkylaryl, or aromatic(including heteroaromatic) groups.

In some embodiments, substituted alkyls can include a heterocyclicgroup. As used herein, the term “heterocyclic group” includes closedring structures analogous to carbocyclic groups in which one or more ofthe carbon atoms in the ring is an element other than carbon, forexample, nitrogen, sulfur or oxygen. Heterocyclic groups may besaturated or unsaturated. Exemplary heterocyclic groups include, but arenot limited to, aziridine, ethylene oxide (epoxides, oxiranes), thiirane(episulfides), dioxirane, azetidine, oxetane, thietane, dioxetane,dithietane, dithiete, azolidine, pyrrolidine, pyrroline, oxolane,dihydrofuran, and furan.

The term “polyol ester” refers to an ester of an organic compoundcontaining at least two hydroxyls with at least one carboxylic acid.

The term “surfactant” refers to a molecule having surface activity,including wetting agents, dispersants, emulsifiers, detergents, andfoaming agents, and the like. It is understood to be inclusive of theuse of a single surfactant or multiple surfactants.

The term “water miscible” as used herein, means the component (e.g.,solvent) is soluble or dispersible in water at about 20° C. at aconcentration greater than about 0.2 g/L, preferably at about 1 g/L orgreater, more preferably at 10 g/L or greater, and most preferably atabout 50 g/L or greater.

The term “weight percent,” “wt. %,” “wt-%,” “percent by weight,” “% byweight,” and variations thereof, as used herein, refer to theconcentration of a substance as the weight of substance divided by thetotal weight of the composition and multiplied by 100.

As used herein, the term “free of a compound” refers to a composition,mixture, or ingredient does not contain the compound or to which thecompound has not been added. Should the compound be present throughcontamination of a composition, mixture, or ingredients free of thecompound, the amount of the compound shall be less than 0.5 wt %. Morepreferably, the amount of the compound is less than 0.1 wt-%, and mostpreferably, the amount of phosphate is less than 0.01 wt %. In thisdisclosure, the compound the disclosed conductive coating composition isfree of can be a surfactant, additive, or combination thereof.

As used herein, the term “an existing conductive coating composition”refers to a conductive coating composition does not contain anyfunctionalized carbon nanomaterial or boron nanomaterial. Such anexisting conductive coating composition can contain non-functionalizedcarbon nanomaterial.

The methods, systems, apparatuses, and compositions of the presentinvention may comprise, consist essentially of, or consist of thecomponents and ingredients of the present invention as well as otheringredients described herein. As used herein, “consisting essentiallyof” means the methods, systems, apparatuses and compositions may includeadditional steps, components or ingredients, but only if the additionalsteps, components or ingredients do not materially alter the basic andnovel characteristics of the claimed methods, systems, apparatuses, andcompositions.

Further terms are defined in the detailed description.

Conductive Coating Compositions

The conductive coating compositions comprise a fluid capable of hydrogenbonding and a nanomaterial. Preferred fluids capable of hydrogenbonding, include, a fluid component capable of hydrogen bonding. Thenanomaterials can be capable of hydrogen bonding or not capable ofhydrogen bonding. Preferred nanomaterials are those functionalizedhaving one or more of a first functional group capable of forming anelectrostatic attraction, including, but not limited to, a hydrogen bondor boron nanomaterial; and wherein the fluid comprises one or more of asecond functional group capable of forming an electrostatic attraction,including, but not limited to, a hydrogen bond with the first functiongroup of the nanomaterial. Preferably, the conductive coatingcomposition is stable. Preferably, the conductive coating composition isflexible. Preferably, the conductive coating material is paintable andwill adhere to a surface as a coating material does not crack.Non-limiting, exemplary conductive coating compositions are shown theTable 3.

TABLE 3 First Second Third Exemplary Exemplary Exemplary CompositionComposition Composition (wt. %) (wt. %) (wt. %) Fluid Component  25-99.9   50-99.5 75-95 Nanomaterial 0.1-20  0.5-10  0.5-5   OptionalAdditional  0-70  0-47  0-23 Components

The conductive coating compositions preferably have improved electricalconductivity and improved resistance. Preferably, the resistance isimproved (lowered) over the fluid component alone by at least about 10%,20%, 30%, 40%, 50%, 60%, 70%, 80% when measured by the same test underthe same conditions. Preferably, the electrical conductivity is improved(increased) over the fluid component alone by at least about 10%, 20%,50%, 100%, 200%, 250%, 300%, 400%, 500%, when measured by the same testunder the same conditions.

The conductive coating compositions preferably have improved thermalconductivity. Preferably, the thermal conductivity is improved(increased) over the fluid component alone by at least about 10%, 20%,30%, 40%, 50%, 60%, 70% 80%, 90% 100%, 150%, 200%, 250%, 300%, 350%,when measured by the same test under the same conditions.

The conductive coating compositions can optionally comprise one or moreadditional components added to provide properties to the coatingcompositions. For example, such components can include conductiveparticles, dyes, reflective materials, surfactants, viscosity modifiers,or combinations or mixtures thereof. Other additional components canalso be added.

Fluid Component

The conductive coating compositions and methods described hereincomprise a fluid component comprises a polymer. Preferably, the polymeris a self-curing polymer. Preferably, the polymer is a thermoset polymeror a thermoplastic polymer. In some embodiments, the polymer comprises apolyacrylic acid, a methacrylate (such as poly (methyl methacrylate)),an acrylamide, a nylon, a polyethylene, a polyvinyl chloride, polyol, apolyurethane, an epoxy (preferably, a water-based epoxy), or a mixtureor combination thereof. In some embodiments, the fluid component is anexisting coating composition.

In a preferred embodiment, the fluid component can further comprisewater, a water miscible solvent, an alcohol, or a mixture thereof.Preferred alcohols for incorporation in the fluid component include, butare not limited to, those having a carbon chain between 2 and 20carbons. Particularly preferred alcohols include, but are not limited toethanol, methanol, isopropyl alcohol, and mixtures thereof. Preferredwater miscible solvents include, but are not limited to,dimethylformamide, tetrahydrofuran, and mixtures thereof.

Preferably, the polymer comprises between about 1 wt. % and about 100wt. % of the fluid component, more preferably between about 5 wt. % andabout 95 wt. % of the fluid component, still more preferably betweenabout 10 wt. % and about 90 wt. % of the fluid component, yet morepreferably between about 15 wt. % and about 85 wt. % of the fluidcomponent, even more preferably between about 20 wt. % and about 80 wt.% of the fluid component.

In some embodiments, the composition comprises from about 25 wt-% toabout 99 wt-% of the fluid component. In some other embodiments, thecomposition comprises from about 25 wt-% to about 90 wt-%, from about 25wt-% to about 85 wt-%, from about 25 wt-% to about 80 wt-%, from about25 wt-% to about 75 wt-%, from about 25 wt-% to about 70 wt-%, fromabout 25 wt-% to about 65 wt-%, from about 25 wt-% to about 60 wt-%,from about 25 wt-% to about 55 wt-%, from about 25 wt-% to about 50wt-%, from about 25 wt-% to about 45 wt-%, from about 25 wt-% to about40 wt-%, from about 25 wt-% to about 35 wt-%, from about 25 wt-% toabout 30 wt-%, from about 30 wt-% to about 99 wt-%, from about 35 wt-%to about 99 wt-%, from about 45 wt-% to about 99 wt-%, from about 55wt-% to about 99 wt-%, from about 65 wt-% to about 99 wt-%, from about75 wt-% to about 99 wt-%, from about 80 wt-% to about 99 wt-%, fromabout 85 wt-% to about 99 wt-%, from about 99 wt-% to about 99 wt-%,from about 25 wt-% to about 95 wt-%, from about 35 wt-% to about 95wt-%, from about 45 wt-% to about 95 wt-%, from about 55 wt-% to about95 wt-%, from about 65 wt-% to about 95 wt-%, from about 75 wt-% toabout 95 wt-%, from about 85 wt-% to about 95 wt-%, from about 25 wt-%to about 85 wt-%, from about 35 wt-% to about 75 wt-%, from about 45wt-% to about 65 wt-%, from about 55 wt-% to about 60 wt-%, about 25wt-%, about 35 wt-%, about 40 wt-%, about 45 wt-%, about 55 wt-%, about60 wt-%, about 65 wt-%, about 70 wt-%, about 75 wt-%, about 80 wt-%,about 85 wt-%, about 90 wt-%, about 95 wt-%, about 99 wt-%, or any valuetherebetween of the fluid component.

In another aspect, the present disclosure is a method of enhancingthermal or electric conductivity and/or resistance of a conductivecoating composition, the method comprises adding into a coatingcomposition a nanomaterial to form an improved coating composition,wherein the nanomaterial is a functionalized carbon nanomaterial havingone or more of a first functional group capable of forming anelectrostatic attraction, including, but not limited to, a hydrogen bondwith a second functional group in the coating composition or boronnanomaterial.

In some other embodiments the method further comprising adding water ora fluid component, wherein the fluid component comprises a functionalgroup capable of forming an electrostatic attraction, including, but notlimited to, a hydrogen bond with the first functional group of thenanomaterial.

Nanomaterials

The conductive coating compositions comprise a nanomaterial. In someembodiments, the nanomaterial is capable of hydrogen bonding. In someembodiments, the nanomaterial is not capable of hydrogen bonding. Insome embodiments, the nanomaterial comprises a carbon nanomaterial,boron nanomaterial, or combination thereof. In some embodiments, thenanomaterial comprises a carbon nanofiber, a single-walled carbon,multiple-walled carbon, single-walled boron, multiple-walled boronnanomaterial, or combination thereof.

Preferred nanomaterials are those functionalized having one or more of afirst functional group capable of forming an electrostatic attraction,including, but not limited to, a hydrogen bond or boron nanomaterial;and wherein the fluid comprises one or more of a second functional groupcapable of forming an electrostatic attraction, including, but notlimited to, a hydrogen bond with the first function group of thenanomaterial. Preferred nanomaterials include, but are not limited to,carbon particles and boron nanomaterials.

In some embodiments, the first and second functional group is ahydrophilic functional group. In some other embodiments, the first andsecond function group are independently —OH, —NH, —COOH, —F, —BH, —O—,—N—, or combination thereof. In yet some other embodiments, the firstfunctional group is sulfonate, carboxyl, hydroxyl, amino, amide, urea,carbamate, urethane, or phosphate and the second functional group is—OH, —NH, —COOH, —F, —BH, —O—, —N—, or combination thereof. In someembodiments, the fluid component comprises at least one compound have atleast one functional group can form an electrostatic attraction,including, but not limited to, a hydrogen bond with at least onefunctional group in a functionalized carbon nanomaterial or boronnanomaterial.

In some embodiments, the nanomaterial is carbon nanomaterial. In someother embodiments, the nanomaterial is carbon nanotube. In someembodiments, the nanomaterial is a single-walled, multiple-wallednanotube, or a mixture thereof. In some other embodiments, thenanomaterial is a OH functionalized carbon nanomaterial. In yet someother embodiments, the nanomaterial is a fluorine functionalized carbonnanomaterial.

In some embodiments, the nanomaterial is a OH functionalized carbonmulti-walled nanotube. In some other embodiments, the nanomaterial is afluorine functionalized carbon multi- walled nanotube. In yet some otherembodiments, the nanomaterial is a OH functionalized carbonsingle-walled nanotube. In some other embodiments, the nanomaterial is afluorine functionalized carbon single-walled nanotube.

In some embodiments, the nanomaterial is boron nanomaterial. In someother embodiments, the nanomaterial is a single-walled boron nanotube.In yet some other embodiments, the nanomaterial is a multiple-walledboron nanotube.

In some embodiments, the nanomaterial comprises both carbon and boronnanomaterial. In some other embodiments, wherein the nanomaterialcomprises both carbon and boron nanotubes. In some other embodiments,the nanomaterial comprises single-walled carbon, multiple-walled carbon,single-walled boron, multiple-walled boron nanotube, or a combinationthereof.

In some embodiments, the improved coating composition comprises fromabout 0.1 wt-% to about 20 wt-% of the nanomaterial, more preferablybetween about 0.5 wt % and about 10 wt. %, still more preferably fromabout 0.1 wt-% to about 5-% of the nanomaterial. In some otherembodiments, wherein the composition comprises from about 0.5 wt-% toabout 3 wt-% of the nanomaterial. In yet some other embodiments, thecomposition comprises from about 0.5 wt-% to about 2 wt-% of thenanomaterial. In some other embodiments, the composition comprises fromabout 0.5 wt-% to about 1.5 wt-% of the nanomaterial.

Carbon Particles and Boron Nanomaterials

The conductive coating composition and methods of making the samecomprise carbon particles and/or boron nanomaterials. The carbonparticles are preferably nanoparticles or nanomaterials. As used hereinthe reference to nanoparticles or nanomaterials (carbon or boron)includes particles or materials having at least one dimension is lessthan 10,000 nanometers. Preferably, the nanoparticles and/ornanomaterials have at least one dimension less than 5000 nanometers,more preferably 1000 nanometers, still more preferably less than 750nanometers, even more preferably less than 500 nanometers, and mostpreferably less than 250 nanometers. The terms “nanoparticle” and“nanomaterial” include, for example “nanospheres,” “nanorods,”“nanocups,” “nanowires,” “nanoclusters,” “nanofibers,” “nanolayers,”“nanotubes,” “nanocrystals,” “nanobeads,” “nanobelts,” and “nanodisks.”

The terms “carbon nanoparticle” and “carbon nanomaterial” refer to ananoparticle or nanomaterial which contain primarily carbon element,including, but not limited to, diamond, graphite, fullerenes, carbonnanotubes, carbon fibers, and combinations thereof. Similarly, the terms“boron nanoparticle” and “boron nanomaterial” refers to a nanoparticleor nanomaterial which primarily contain boron element or boroncompounds.

The term “nanotube” refers to a class of nanoparticle or nanomaterialwhich have a shape of a long thin cylinder and contain primarily carbonelement. The term “aspect ratio” refers to a ratio of the length overthe diameter of a particle. The term “SWNT” refers to a single-wallednanotube. The term “MWNT” refers to a multi-walled nanotube. The term“D-WNT” refers to a double-walled nanotube. The term “F-SWNT” refers toa fluorinated SWNT.

Similarly, the term “carbon nanotube” refers to a class of carbonnanoparticle which have a shape of a long thin cylinder and containprimarily carbon element. The term “boron nanotube” refers to a class ofboron nanoparticle which have a shape of a long thin cylinder andcontain primarily carbon element. Both carbon and boron nanotube can bemulti-wall or single walled nanotube.

Carbon nanotubes (“CNT”) are nanoparticles in the shape of a long thincylinder often with a diameter in few nanometers. The basic structuralelement in a carbon nanotube is a hexagon which is the same as found ingraphite. Based on the orientation of the tube axis with respect to thehexagonal lattice, a carbon nanotube can have three differentconfigurations: armchair, zigzag, and chiral (also known as spiral). Inarmchair configuration, the tube axis is perpendicular to two of sixcarbon-carbon bonds of the hexagonal lattice. In zigzag configuration,the tube axis is parallel to two of six carbon-carbon bonds of thehexagonal lattice. Both these two configurations are achiral. In chiralconfiguration, the tube axis forms an angle other than 90 or 180 degreeswith any of six carbon-carbon bonds of the hexagonal lattice.

Carbon nanotubes of these configurations often exhibit differentphysical and chemical properties. For example, an armchair nanotube isalways metallic whereas a zigzag nanotube can be metallic orsemi-conductive depending on the diameter of the nanotube. All threedifferent nanotubes are expected to be very good thermal conductorsalong the tube axis, exhibiting a property known as “ballisticconduction,” but good insulators laterally to the tube axis.

In addition to the common hexagonal structure, the cylinder of a carbonnanotube molecule can also contain other size rings, such as pentagonand heptagon. Replacement of some regular hexagons with pentagons and/orheptagons can cause cylinders to bend, twist, or change diameter, andthus lead to some interesting structures such as “Y-,” “T-,” and“X-junctions,” and different chemical activities. Those variousstructural variations and configurations can be found in both SWNT andMWNT. However, the present invention is not limited by any configurationand structural variation. The carbon nanotube used in the presentinvention can be in the configuration of armchair, zigzag, chiral, orcombinations thereof. The carbon nanotube can also contain structuralelements other than hexagon, such as pentagon, heptagon, octagon, orcombinations thereof.

Another structural variation for MWNT molecules is the arrangement ofthe multiple tubes. A perfect MWNT is like a stack of graphene sheetsrolled up into concentric cylinders with each wall parallel to thecentral axis. However, the tubes can also be arranged so an anglebetween the graphite basal planes and the tube axis is formed. Such MWNTis known as a stacked cone, Chevron, bamboo, ice cream cone, or piledcone structures. A stacked cone MWNT can reach a diameter of about 1 00nm. Despite these structural variations, all MWNTs are suitable for thepresent invention if they have an excellent thermal conductivity. Theterm MWNT used herein also includes double-walled nanotubes (“D-WNT”).

In some embodiments, the carbon nanotubes are single-walled nanotubes(“SWNT”), double-walled nanotubes (“DWNT”), multi-walled nanotubes(“MWNT”), or a combination of the same. In some other embodiment, thecarbon nanotubes include carbon SWNT, MWNT, and/or DWNT. As used herein,the term MWNT is inclusive of DWNTs.

In some embodiments, the boron nanotubes are single-walled nanotubes(“SWNT”), double-walled nanotubes (“DWNT”), multi-walled nanotubes(“MWNT”), or a combination of the same. In some other embodiment, theboron nanotubes include boron SWNT, MWNT, and/or DWNT.

Carbon or boron nanotubes used in the present invention can alsoencapsulate other elements and/or molecules within their enclosedtubular structures. Such elements include Si, Ti, V, Cr, Mn, Fe, Co, Ni,Cu, Y, Zr, Mo, Ta, Au, Th, La, Ce, Pr, Nb, Gd, Tb, Dy, Ho, Er, Tm, Yb,Lu, Mo, Pd, Sn, and W. Carbon nanotubes used in the present disclosurealso include alloys of these elements such as alloys of cobalt with S,Br, Pb, Pt, Y, Cu, B, and Mg, and compounds such as the carbides (i.e.TiC, MoC, etc.) The present of these elements, alloys and compoundswithin the core structure of fullerenes and nanotubes can enhance thethermal conductivity of these nanotubes which then translates to ahigher thermal conductive nanofluid when these nanotubes are suspend ina heat transfer fluid.

Carbon nanotubes used in the present invention can also be chemicallymodified and functionalized to be so-called “functionalized carbonnanotubes”, such as covalently attached hydrophilic groups to increasetheir solubility in hydrophilic fluids or lipophilic chains to increasetheir solubility in hydrophobic oils. Covalent functionalization ofcarbon nanotubes, especially fullerenes, has commonly been accomplishedby three different approaches, namely, thermally activated chemistry,electrochemical modification, and photochemical functionalization. Themost common methods of thermally activated chemical functionalizationare addition reactions on the sidewalls. For example, the extensivetreatment of a nanotube with concentrated nitric and sulfuric acidsleads to the oxidative opening of the tube caps as well as the formationof holes in the sidewalls and thus produces a nanotube decorated withcarboxyl groups, which can be further modified through the creation ofamide and ester bonds to generate a vast variety of functional groups.

The carbon nanotube can also be modified through addition reactions withvarious chemical reagents such halogens and ozone. Unlike thermallycontrolled modification, electrochemical modification of carbonnanotubes can be carried out in more selective and controlled manner.Interestingly, a SWNT can be selectively modified or functionalizedeither on the cylinder sidewall or the optional end caps. These twodistinct structural moieties often display different chemical andphysical characteristics. The functional group on functionalized carbonnanotubes may be attached directly to the carbon atoms of a carbonnanotubes or via chemical linkers, such as alkylene or arylene groups.To increase hydrophilicity, carbon nanotubes can be functionalized withone or more hydrophilic functional groups, such as, sulfonate, carboxyl,hydroxyl, amino, amide, urea, carbamate, urethane, and phosphate. Toincrease hydrophobicity, carbon nanoparticles may be functionalized withone or more hydrophobic alkyl or aryl groups. The functionalized carbonnanoparticle may have no less than about 2, no less than about 5, noless than about 10, no less than about 20, or no less than about 50functional groups on average.

The term “carbon nanotube” or “boron nanotube” used herein refers to allstructural variations and modification of SWNT and MWNT discussedhereinabove, including configurations, structural defeats andvariations, tube arrangements, chemical modification andfunctionalization, and encapsulation.

To some extent, any carbon nanomaterial can be chemically modified orfunctionalized to become a “functionalized carbon nanomaterial”, in asimilar way for carbon nanotubes.

Carbon nanotubes are commercially available from a variety of sources.Single walled carbon nanotubes can be obtained from Carbolex (Broomall,Pa.), MER Corporation (Tucson, Ariz.), and Carbon NanotechnologiesIncorporation (“CNI”, Houston, Tex.). Multi-walled carbon nanotubes canbe obtained from MER Corporation (Tucson, Ariz.) and Helix materialsolution (Richardson, Tex.). However, the present invention is notlimited by the source of carbon nanotubes. In addition, manypublications are available with enough information to allow one tomanufacture nanotubes with desired structures and properties. The mostcommon techniques are arc discharge, laser ablation, chemical vapordeposition, and flame synthesis. In general, the chemical vapordeposition has shown the most promise in being able to produce largerquantities of nanotubes at lower cost. This is usually done by reactinga carbon containing gas, such as acetylene, ethylene, ethanol, etc.,with a metal catalyst particle, such as cobalt, nickel, or ion, attemperatures above 600° C.

The selection of a carbon nanomaterial depends on several factors. Themost important factor is the carbon nanomaterial is a functionalizedcarbon nanomaterial having one or more functional groups forming ahydrogen bond with another functional group existing in an alreadyexisting fluid component or just co-existing fluid component. Boronnanomaterial can generally form hydrogen bond with another functionalgroup capable of forming hydrogen bond.

Another important consideration is the nanomaterial must be compatiblewith an already existing fluid component discussed thereafter. Otherfactors include heat transfer properties, electrical transferproperties, cost effectiveness, solubility, dispersion and settlingcharacteristics. In some embodiments of the present disclosure, thecarbon nanomaterial selected contain predominantly single-walledfunctionalized carbon nanotubes. In some other embodiments, thenanomaterial selected contain predominantly multi-walled functionalizedcarbon nanotubes. In some embodiments of the present disclosure, thecarbon nanomaterial selected contain predominantly single-walled boronnanotubes. In some other embodiments, the nanomaterial selected containpredominantly multi-walled boron nanotubes.

In one aspect, the carbon nanotube has a carbon content of no less thanabout 60%, no less than about 80%, no less than about 90%, no less thanabout 95%, no less than about 98%, or no less than about 99%.

In another aspect, the carbon or boron nanotube has a diameter of fromabout 0.2 to about 100 nm, from about 0.4 to about 80 nm, from about 0.5to about 60 nm, or from about 0.5 to about 50 nm. In yet another aspect,the carbon nanotube is no greater than about 200 micrometers, no greaterthan 100 micrometers, no greater than about 50 micrometers, or nogreater than 20 micrometers in length. In yet another aspect, the carbonnanotube has an aspect ratio of not greater than 1,000,000, no greaterthan 100,000, no greater than 10,000, no greater than 1,000, no greaterthan about 500, no greater than about 200, or no greater than about 100.

Dyes

In some embodiments, the conductive coating composition can include oneor more dyes or components added to impart a color. In some embodiments,the conductive coating compositions can be free of a dye. If a dye isincluded, it is preferably in an amount between about 0.001 wt. % andabout 35 wt. %.

Reflective Material

In some embodiments, the conductive coating composition can include areflective material. Preferred reflective materials include reflectiveparticles. In some embodiments, the conductive coating compositions canbe free of a reflective particle. If a reflective material is included,it is preferably in an amount between about 0.001 wt. % and about 25 wt.%.

Surfactants

The conductive coating composition can include a surfactant or be freeof surfactant. Surfactants suitable for use with the compositions of thepresent invention include, but are not limited to, nonionic surfactants,anionic surfactants, and zwitterionic surfactants. In some embodiments,the compositions of the present invention include about 0.001 wt % toabout 30 wt. % of a surfactant. In other embodiments the compositions ofthe present invention include about 0.1 wt. % to about 25 wt. % of asurfactant. In still yet other embodiments, the compositions of thepresent invention include between about 1 wt. % and about 15 wt. % of asurfactant.

Viscosity Modifiers

The conductive coating composition can optionally comprise a viscositymodifier. Preferred viscosity modifiers include thickeners or thinners.

Methods of Preparing the Conductive Coating Compositions

The conductive coating compositions can be prepared with a variety ofequipment and under conditions specific to the ingredients for theconductive coating composition. For example, the method may includeheating the fluid, such carbon particles and/or boron nanomaterials canbe dispersed therein. The precise temperature of the heating may bedictated by the melting point or boiling point of the fluid.

The conductive coating compositions can be prepared in batch orcontinuous processes. To prepare the conductive coating compositions,the fluid can be heated. In some embodiments the fluid component isheated; in some embodiments the fluid component is not heated. Whetherthe fluid component is heated can depend on the type of polymer includedin the fluid component. For example, a polymer such as a thermoset maycure upon heating. The temperature of heating may vary based on thefluid component and species of polymer in the fluid component. In anembodiment, where the fluid component is heated, it is preferably heatedto a temperature between about 20° C. and about 100° C., more preferablya temperature between about 23° C. and about 90° C. In some embodiments,heating is not necessary.

After heating the fluid component, carbon particles and/or boronnanomaterials can be added to the fluid component. The carbon particlesand/or boron nanomaterials can be added all at once or sequentially insmaller portions. Preferably, the carbon particles and/or boronnanomaterials are mixed or stirred in the fluid to form a conductivecoating composition. If the carbon particles and/or boron nanomaterialsare added sequentially in small portions, the mixing and/or stirring canbe performed as the nanotubes are being added and/or between sequentialadditions. Preferred mixing and stirring methods, include, but are notlimited to, automatic mixers (such as paddle mixers), stir bars, manualstirring or manual mixing, sonication, etc. The intensity and speed ofthe mixing or stirring can vary. Preferably, the intensity and/or speedare not too vigorous to break or degrade the carbon particle and/orboron nanomaterial structures. The stirring can occur for any amount oftime enough to disperse the carbon particles and/or boron nanomaterials.Preferably, the carbon particles and/or boron nanomaterials arethoroughly dispersed; most preferably, the carbon particles and/or boronnanomaterials are homogenously dispersed in the fluid. Preferred mixingand/or stirring times can be between about 1 minute and 2 hours; morepreferably, between about 2 minutes and about 1 hour; most preferablybetween 5 minutes and 30 minutes. In an embodiment where the preparationof the conductive coating compositions is a continuous process, themixing may be continuous.

After mixing, the conductive coating composition can optionally beheated, cooled, or maintained at the same temperature. If the conductivecoating composition is heated, it is preferably heated to a temperaturebetween about 20° C. and about 100° C., more preferably to a temperaturebetween about 230° C. and about 90° C. The heating can be performed fora time between about 1 minute and about 2 hours; more preferably betweenabout 5 minutes and about 90 minutes; most preferably between about 10minutes and about 1 hour.

Preferably the conductive coating composition is passed through a rollermill, an extruder, a manual or mechanical stirrer. Preferably, theconductive coating composition is passed through a roller mill.Preferred roller mills include, but are not limited to, two-roll millsand three-roll mills. Preferably the conductive coating composition ispassed through a roller mill enough times to obtain a smoothconsistency. In a preferred method, the conductive coating compositionis passed through a roller mill between 1 and 20 times, more preferablybetween 2 and 15 times, most preferably between 3 and 10 times. Theconductive coating composition can be passed through the same rollermill multiple times or through a series of roller mills to achieve thedesired number of pass-throughs.

After passing the conductive coating composition through a roller mill,the conductive coating composition can be heated, cooled, or maintainedat the same temperature. The conductive coating composition can then beapplied to a surface. Suitable methods of applying the conductivecoating material to surface include, but are not limited to, painting,printing, spraying, manual application methods, automated or machineapplication methods, or a combination thereof. Preferred printingmethods include, but are not limited to 3D printing, inkjet printing,and Sonitek® printing.

After the conductive coating compositions are applied to a surface, theconductive coating compositions can be cured. Preferred methods ofcuring include, self-curing, UV curing, thermal curing (e.g., heating),free radical curing, or a combination thereof.

While an understanding of the mechanism is not necessary to practice thepresent invention and while the present invention is not limited to anymechanism of action, it is contemplated the combination of a fluid andnanomaterial can form an electrostatic attraction, including, but notlimited to, a hydrogen bond among them leads to enhanced thermal andelectrical conductivity. Because of this combination, the disclosedcoating compositions herein possess an enhanced thermal and/orelectrical conductivity. The disclosed coating compositions are alsomore stable even under tough conditions.

All publications and patent applications in this specification areindicative of the level of ordinary skill in the art to which thisinvention pertains. All publications and patent applications are hereinincorporated by reference to the same extent as if each individualpublication or patent application was specifically and individuallyindicated as incorporated by reference.

EXAMPLES

Embodiments of the present invention are further defined in thefollowing non-limiting Examples. These Examples, while indicatingcertain embodiments of the invention, are given by way of illustrationonly. From the above discussion and these Examples, one skilled in theart can ascertain the essential characteristics of this invention, andwithout departing from the spirit and scope thereof, can make variouschanges and modifications of the embodiments of the invention to adaptit to various usages and conditions. Thus, various modifications of theembodiments of the invention, in addition to those shown and describedherein, will be apparent to those skilled in the art from the foregoingdescription. Such modifications are also intended to fall within thescope of the appended claims.

Example 1

In this Example, a series of flexible nanocoating compositions wereprepared and some electrical and/or thermal properties were measured. Anexemplary procedure for making the flexible nanocoating compositionsfollows. The exemplary compositions were prepared according to thisexemplary method. The fluid component was heated to increase theviscosity and facilitate better mixing of the materials. Carbonnanomaterials were slowly added to the fluid component while stirring.Once all carbon nanotubes were added, the mixture was stirred for 10more minutes. The mixture could cool down while stirring until it issafe to handle. The mixture was passed through a three-roll mill eighttimes to obtain a smooth consistency.

Table 4 lists the ingredients and the measured resistances. Theresistivity was measured with a Keithly instrument 2401. The accurateresistivity was measured with a four-probe meter. The thermalconductivity data was obtained using the Hot Disk™ thermal constantsanalyzer, using the following parameters:

measurement depth: 6 mm

room temperature: 25° C.

power: 0.025 W

measurement time: 16 seconds

sensor radius: 2.001 mm

TCR: 0.0471/K,

disk type: Kapton

temperature drift rec: yes

TABLE 4 The ingredients and measured resistance of some exemplarycoatings. Accurate Thermal Fluid Carbon Resistivity ResistivityConductivity Component Carbon wt. % (ohm) (Ω · m) (W/mK)_(cured)Polyurethane MWNT-OH 7.5 (#50) 400 Polyurethane MWNT-OH 5 (#51) 6000Polyacrylic MWNT-OH 5 1.6 × 10⁴ Polyurethane MWNT-OH 2 8.9 × 10⁴Polyurethane MWNT-OH 4.5 1.3 × 10² (#57) 75 wt. %/ 25 wt. % H₂OPolyurethane MWNT-OH 7.5 1.3 × 10² diluted w/H₂O Polyurethane MWNT-OH7.5 5.7 × 10² (9.25 g grease diluted w/4 g H2O) Polyurethane MWNT-OH 4.55.8 × 10³ 75 wt. % MWNT-OH 4.5 1.2 × 10^(x3) Polyacrylic/25 wt. % H₂O 75wt. % MWNT-OH 4.5 4.8 × 10² (#55) 25 Polyurethane/ 25 wt. % IPA 75 wt. %MWNT-OH 4.5 2.1 × 10² (#56) 6.8 Polyurethane/ 25 wt. % EtOH A + B WaterMWNT-OH 5 5.8 × 10^(x3) Based Epoxy Thick to MWNT-OH N/A (#54) 23.2Diluted Polyurethane Polyurethane CNF-19 10 3.4 × 10^(x1) 1.578 50 wt. %CNF-19 10   1 × 10^(x1) 1.254 Polyurethane/ 50 wt. % H₂O

The stability of the coating compositions was assessed visually. Ifunstable the components would separate. This was not observed for any ofthe exemplary samples prepared and examined. All the coatings werestable and maintained conductivity over several months.

As shown in Table 4, many of the coating compositions provided excellentresistivity properties. These results demonstrate the coatingcompositions described herein could be useful as conductive coatingmaterials.

Example 2

An exemplary coating composition was prepared and painted onto a surfaceto assess its paintability and its ability to serve as a surfacecoating. The compositions comprised 25 wt. % ethanol and 75 wt. %Polyurethane as the fluid component and had 4.5 wt. % of MWNT-OH carbonnanomaterials. The properties of this composition are reflected in Table4. The photograph of the coating painted onto the surface can be seen inFIGS. 25A and 25B.

As can be seen in FIGS. 25A and 25B, the coating composition was capableof painting on a surface. It covered the surface and dried withoutcracking or peeling from the surface. Inspection of the composition onthe surface revealed its suitability to serve as a coating material.

Therefore, various methods, systems, and apparatus have been shown anddescribed. Although various embodiments or examples have been set forthherein, it is to be understood the present invention contemplatesnumerous options, variations, and alternatives as may be appropriate inan application or environment.

What is claimed is:
 1. A non-volatile memory circuit, comprising: alogic source; and a semi-conductive device being electrically coupled tothe logic source, having a first terminal, a second terminal and anano-grease located between the first and second terminal, wherein thenano-grease exhibits non-volatile memory characteristics.
 2. Thenon-volatile memory circuit of claim 1, wherein the nano-grease exhibitsmemristive properties.
 3. The non-volatile memory circuit of claim 1,wherein the nano-grease exhibits memcapacitive properties.
 4. Thenon-volatile memory circuit of claim 1, wherein the nano-grease exhibitsmeminductive properties.
 5. The non-volatile memory circuit of claim 2,wherein the nano-grease can store the last known current through thenano-grease.
 6. The non-volatile memory circuit of claim 3, wherein thenano-grease can store the last known charge held by the nano-grease. 7.The non-volatile memory circuit of claim 4, wherein the nano-grease canstore the last known current passing through the nano-grease.
 8. Thenon-volatile memory circuit of claim 1, wherein the nano-greasecomprises less than 2.5% by weight of single wall carbon nanotubes(SWNT).
 9. The non-volatile memory circuit of claim 1, wherein thenano-grease comprises less than 1.5% by weight of multi wall carbonnanotubes.
 10. The non-volatile memory of circuit of claim 1, whereinthe logic source is an analog source.
 11. A non-volatile memory circuit,comprising: a voltage source; a semi-conductive device beingelectrically coupled to the logic source, having a first terminal, asecond terminal and a nano-grease located between the first and secondterminal, wherein the nano-grease exhibits non-volatile memorycharacteristics; and a voltage sensor electrically coupled in parallelwith the semi-conductive device capable of measuring the voltage drop atthe semi-conductive device.
 12. The non-volatile memory circuit of claim11, wherein the nano-grease exhibits memristive properties.
 13. Thenon-volatile memory circuit of claim 11, wherein the nano-greaseexhibits memcapacitive properties.
 14. The non-volatile memory circuitof claim 11, wherein the nano-grease exhibits meminductive properties.15. The non-volatile memory circuit of claim 11, wherein thesemi-conductive device is a digital memory.
 16. The non-volatile memorycircuit of claim 11, wherein the nano-grease is comprised of less than2.5% by weight single wall carbon nanotubes (SWNT).
 17. The non-volatilememory circuit of claim 11, wherein the nano-grease is comprised of lessthan 1.5% by weight multi wall carbon nanotubes (MWNT).
 18. Thenon-volatile memory circuit of claim 11, wherein the terminals comprisesubstantially planar micro- or nano-terminals.
 19. The non-volatilememory circuit of claim 11, fabricated in an integrated microchip. 20.The non-volatile memory circuit of claim 11, wherein each voltage sourceis electrically connected to a non-volatile analog memory.